Handling user plane in wireless systems

ABSTRACT

Systems, methods and instrumentalities may be provided for handling a user plane in a wireless communication system. The wireless communication system may be characterized by a flexible air interface. One aspect of the flexible air interface is that transmissions by a wireless transmit/receive unit (WTRU) in the system may have different quality of service (QoS) requirements, such as different latency requirements. The WTRU may adjust its behaviors based on the QoS requirements, e.g., by utilizing preconfigured resources, resource requests, self-scheduling, and/or the like, such that the transmissions may be performed in accordance with their respective QoS requirements.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the National Stage entry under 35 U.S.C. § 371 ofPatent Cooperation Treaty Application PCT/US2017/024778, filed Mar. 29,2017, which claims the benefit of provisional U.S. patent applicationNo. 62/315,373, filed Mar. 30, 2016, the disclosure of which isincorporated herein by reference in its entirety.

BACKGROUND

Mobile communications are in continuous evolution and is already at thedoorstep of its fifth incarnation—5G. 5G network may be built onflexible radio access technologies. As these new technologies emerge,challenges arise in determining how to support a wide variety of usagecases with differing characteristics.

SUMMARY

Systems, methods and instrumentalities are disclosed herein fortransmitting uplink data from a wireless transmit/receive unit (WTRU) toa network. The uplink data may include an uplink data unit (e.g., anuplink data packet), and the transmission of the uplink data unit may beperformed in a manner that satisfies a specific quality of service (QoS)requirement. The QoS requirement may be a timing requirement. Forexample, the QoS requirement may be that the uplink data unit betransmitted with relatively low latency.

The WTRU may maintain a time-to-live (TTL) parameter to monitor thetransmission latency of the uplink data unit. For example, the value ofthe TTL parameter may be reflective of an amount of time elapsed sincethe uplink data unit became available for transmission and/or an amountof time remaining before the uplink data unit is supposed to besuccessfully transmitted. The WTRU may determine, based on the QoSrequirement, a threshold value for the TTL parameter, attempt totransmit the uplink data unit using a first transmission mode, anddetermine that the value of the TTL parameter has reached a thresholdvalue before a successful transmission can be accomplished. The WTRU maythen try to transmit the uplink data unit using a second transmissionmode, for example until the TTL parameter reaches expiration.

The second transmission mode may differ from the first transmission modein one or more aspects. For example, the WTRU may transmit the uplinkdata unit in the second transmission mode using a pre-configured set ofresources. The WTRU may receive such preconfigured resources, forexample from a network. The network may have reserved the preconfiguredresources for transmissions characterized by a particular QoSrequirement, such as the QoS requirement associated with the pendinguplink data unit. The network may specify that the pre-configuredresources are to be shared by multiple WTRUs.

The WTRU may receive the pre-configured resources when the WTRUinitially registers with the network. Alternatively or additionally, theWTRU may receive the pre-configured resources via dedicated signalingfrom the network (e.g., after the WTRU has already registered with thenetwork). The WTRU may gain access to the pre-configured set ofresources through an uplink transmission to the network. The uplinktransmission may indicate a time at which the WTRU desires to use thepre-configured resources, for example. The WTRU may receive anacknowledgement from the network in response to the uplink transmission.

The WTRU may, in the second transmission mode, send uplink controlinformation (UCI) to the network. The UCI may include a request forresources. The UCI may indicate the QoS requirement associated with theuplink data unit, or a numerology of the uplink data unit. The WTRU mayreceive a grant from the network in response to the UCI. The grant mayindicate which resources the WTRU can use in the second transmissionmode. Additionally or alternatively, the grant may specify a spectrumoperation mode (SOM) or a transport channel that the WTRU can use in thesecond transmission mode. For example, the grant may specify anumerology and/or a waveform that the WTRU can use in the secondtransmission mode.

The WTRU may, in the second transmission mode, interrupt an existinghybrid automatic repeat request (HARQ) process to transmit the uplinkdata unit.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding may be had from the following description,given by way of example in conjunction with the accompanying drawingswherein:

FIG. 1A is a system diagram of an example communications system in whichone or more disclosed embodiments may be implemented.

FIG. 1B is a system diagram of an example wireless transmit/receive unit(WTRU) that may be used within the communications system illustrated inFIG. 1A.

FIG. 1C is a system diagram of an example radio access network and anexample core network that may be used within the communications systemillustrated in FIG. 1A.

FIG. 1D is a system diagram of another example radio access network andan example core network that may be used within the communicationssystem illustrated in FIG. 1A.

FIG. 1E is a system diagram of another example radio access network andan example core network that may be used within the communicationssystem illustrated in FIG. 1A.

FIG. 2 is an illustration of an example of bandwidth flexibility.

FIG. 3 is an illustration of an example of flexible spectrum allocation.

FIG. 4A is an illustration of an example of timing relationships for TDDduplexing.

FIG. 4B is an illustration of an example of timing relationships for FDDduplexing.

FIG. 5 is an illustration of an example of prioritized transmissions.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

A detailed description of illustrative embodiments will now be describedwith reference to the various Figures. Although this descriptionprovides a detailed example of possible implementations, it should benoted that the details are intended to be exemplary and in no way limitthe scope of the application.

The following abbreviations and acronyms will be used in the descriptionof the example embodiments:

Δf Sub-carrier spacing

5gFlex 5G Flexible Radio Access Technology

5gNB 5GFlex NodeB

ACK Acknowledgement

BLER Block Error Rate

BTI Basic TI (in integer multiple of one or more symbol duration)

CB Contention-Based (e.g. access, channel, resource)

CoMP Coordinated Multi-Point transmission/reception

CP Cyclic Prefix

CP-OFDM Conventional OFDM (relying on cyclic prefix)

CQI Channel Quality Indicator

CN Core Network (e.g. LTE packet core)

CRC Cyclic Redundancy Check

CSI Channel State Information

CSG Closed Subscriber Group

D2D Device to Device transmissions (e.g. LTE Sidelink)

DCI Downlink Control Information

DL Downlink

DM-RS Demodulation Reference Signal

DRB Data Radio Bearer

EMBB Enhanced Mobile Broadband

EPC Evolved Packet Core

FBMC Filtered Band Multi-Carrier

FBMC/OQAM A FBMC technique using Offset Quadrature Amplitude Modulation

FDD Frequency Division Duplexing

FDM Frequency Division Multiplexing

FEC Forward Error Correction

ICC Industrial Control and Communications

ICIC Inter-Cell Interference Cancellation

IP Internet Protocol

LAA License Assisted Access

LBT Listen-Before-Talk

LCH Logical Channel

LCG Logical Channel Group

LCP Logical Channel Prioritization

LLC Low Latency Communications

LTE Long Term Evolution e.g. from 3GPP LTE R8 and up

MAC Medium Access Control

NACK Negative ACK

MBB Massive Broadband Communications

MC MultiCarrier

MCS Modulation and Coding Scheme

MIMO Multiple Input Multiple Output

MTC Machine-Type Communications

NAS Non-Access Stratum

OFDM Orthogonal Frequency-Division Multiplexing

OFDMA Orthogonal Frequency-Division Multiple Access

OOB Out-Of-Band (emissions)

PBR Prioritized Bit Rate

P_(cmax) Total available UE power in a given TI

PHY Physical Layer

PRACH Physical Random Access Channel

PDU Protocol Data Unit

PER Packet Error Rate

PL Path Loss (Estimation)

PLMN Public Land Mobile Network

PLR Packet Loss Rate

PSS Primary Synchronization Signal

QoS Quality of Service (from the physical layer perspective)

RAB Radio Access Bearer

RACH Random Access Channel (or procedure)

RF Radio Front end

RNTI Radio Network Identifier

RRC Radio Resource Control

RRM Radio Resource Management

RS Reference Signal

RTT Round-Trip Time

SCMA Single Carrier Multiple Access

SDU Service Data Unit

SOM Spectrum Operation Mode

SS Synchronization Signal

SSS Secondary Synchronization Signal

SRB Signaling Radio Bearer

SWG Switching Gap (in a self-contained subframe)

TB Transport Block

TBS Transport Block Size

TDD Time-Division Duplexing

TDM Time-Division Multiplexing

TI Time Interval (in integer multiple of one or more BTI)

TTI Transmission Time Interval (in integer multiple of one or more TI)

TRP Transmission/Reception Point

TRx Transceiver

UFMC Universal Filtered MultiCarrier

UF-OFDM Universal Filtered OFDM

UL Uplink

URC Ultra-Reliable Communications

URLLC Ultra-Reliable and Low Latency Communications

V2V Vehicle to vehicle communications

V2X Vehicular communications

WLAN Wireless Local Area Networks and related technologies (IEEE 802.xxdomain)

WTRU Wireless Transmit/Receive Unit

FIG. 1A is a diagram of an example communications system 100 in whichone or more disclosed embodiments may be implemented. The communicationssystem 100 may be a multiple access system that provides content, suchas voice, data, video, messaging, broadcast, etc., to multiple wirelessusers. The communications system 100 may enable multiple wireless usersto access such content through the sharing of system resources,including wireless bandwidth. For example, the communications systems100 may employ one or more channel access methods, such as code divisionmultiple access (CDMA), time division multiple access (TDMA), frequencydivision multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrierFDMA (SC-FDMA), orthogonal frequency-division multiplexing with offsetquadrature amplitude modulation (OFDM-OQAM), universal filteredorthogonal frequency-division multiplexing (UF-OFDM), and the like.

As shown in FIG. 1A, the communications system 100 may include wirelesstransmit/receive units (WTRUs) 102 a, 102 b, 102 c, and/or 102 d (whichgenerally or collectively may be referred to as WTRU 102), a radioaccess network (RAN) 103/104/105, a core network 106/107/109, a publicswitched telephone network (PSTN) 108, the Internet 110, and othernetworks 112, though it will be appreciated that the disclosedembodiments contemplate any number of WTRUs, networks, and/or networkelements.

The communications systems 100 may also include a number of basestations, e.g., base station 114 a and base station 114 b. Each of thebase stations 114 a, 114 b may be any type of device configured towirelessly interface with at least one of the WTRUs 102 a, 102 b, 102 c,102 d to facilitate access to one or more communication networks, suchas the core network 106/107/109, the Internet 110, and/or the networks112. By way of example, the base stations 114 a, 114 b may be a basetransceiver station (BTS), a Node-B, an eNode B, a Home Node B, a HomeeNode B, a site controller, an access point (AP), a wireless router, andthe like. While the base stations 114 a, 114 b are each depicted as asingle element, it will be appreciated that the base stations 114 a, 114b may include any number of interconnected base stations and/or networkelements.

The base station 114 a may be part of the RAN 103/104/105, which mayalso include other base stations and/or network elements (not shown),such as a base station controller (BSC), a radio network controller(RNC), relay nodes, etc. The base station 114 a and/or the base station114 b may be configured to transmit and/or receive wireless signalswithin a particular geographic region, which may be referred to as acell (not shown). The cell may further be divided into cell sectors. Forexample, the cell associated with the base station 114 a may be dividedinto three sectors. Thus, in one embodiment, the base station 114 a mayinclude three transceivers, i.e., one for each sector of the cell. Inanother embodiment, the base station 114 a may employ multiple-inputmultiple output (MIMO) technology and, therefore, may utilize multipletransceivers for each sector of the cell.

The base stations 114 a, 114 b may communicate with one or more of theWTRUs 102 a, 102 b, 102 c, 102 d over an air interface 115/116/117,which may be any suitable wireless communication link (e.g., radiofrequency (RF), microwave, infrared (IR), ultraviolet (UV), visiblelight, etc.). The air interface 115/116/117 may be established using anysuitable radio access technology (RAT).

More specifically, as noted above, the communications system 100 may bea multiple access system and may employ one or more channel accessschemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, OFDM-OQAM, UF-OFDMand the like. For example, the base station 114 a in the RAN 103/104/105and the WTRUs 102 a, 102 b, 102 c may implement a radio technology suchas Universal Mobile Telecommunications System (UMTS) Terrestrial RadioAccess (UTRA), which may establish the air interface 115/116/117 usingwideband CDMA (WCDMA). WCDMA may include communication protocols such asHigh-Speed Packet Access (HSPA) and/or Evolved HSPA (HSPA+). HSPA mayinclude High-Speed Downlink Packet Access (HSDPA) and/or High-SpeedUplink Packet Access (HSUPA).

In another embodiment, the base station 114 a and the WTRUs 102 a, 102b, 102 c may implement a radio technology such as Evolved UMTSTerrestrial Radio Access (E-UTRA), which may establish the air interface115/116/117 using Long Term Evolution (LTE), LTE-Advanced (LTE-A) and/or5gFLEX.

In other embodiments, the base station 114 a and the WTRUs 102 a, 102 b,102 c may implement radio technologies such as IEEE 802.16 (i.e.,Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000,CDMA2000 1×, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), InterimStandard 95 (IS-95), Interim Standard 856 (IS-856), Global System forMobile communications (GSM), Enhanced Data rates for GSM Evolution(EDGE), GSM EDGE (GERAN), and the like.

The base station 114 b in FIG. 1A may be a wireless router, Home Node B,Home eNode B, or access point, for example, and may utilize any suitableRAT for facilitating wireless connectivity in a localized area, such asa place of business, a home, a vehicle, a campus, and the like. In oneembodiment, the base station 114 b and the WTRUs 102 c, 102 d mayimplement a radio technology such as IEEE 802.11 to establish a wirelesslocal area network (WLAN). In another embodiment, the base station 114 band the WTRUs 102 c, 102 d may implement a radio technology such as IEEE802.15 to establish a wireless personal area network (WPAN). In yetanother embodiment, the base station 114 b and the WTRUs 102 c, 102 dmay utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE,LTE-A, 5gFLEX, etc.) to establish a picocell or femtocell. As shown inFIG. 1A, the base station 114 b may have a direct connection to theInternet 110. Thus, the base station 114 b may not be required to accessthe Internet 110 via the core network 106/107/109

The RAN 103/104/105 may be in communication with the core network106/107/109, which may be any type of network configured to providevoice, data, applications, and/or voice over internet protocol (VoIP)services to one or more of the WTRUs 102 a, 102 b, 102 c, 102 d. Forexample, the core network 106/107/109 may provide call control, billingservices, mobile location-based services, pre-paid calling, Internetconnectivity, video distribution, etc., and/or perform high-levelsecurity functions, such as user authentication. Although not shown inFIG. 1A, it will be appreciated that the RAN 103/104/105 and/or the corenetwork 106/107/109 may be in direct or indirect communication withother RANs that employ the same RAT as the RAN 103/104/105 or adifferent RAT. For example, in addition to being connected to the RAN103/104/105, which may be utilizing an E-UTRA radio technology, the corenetwork 106/107/109 may also be in communication with another RAN (notshown) employing a GSM radio technology.

The core network 106/107/109 may also serve as a gateway for the WTRUs102 a, 102 b, 102 c, 102 d to access the PSTN 108, the Internet 110,and/or other networks 112. The PSTN 108 may include circuit-switchedtelephone networks that provide plain old telephone service (POTS). TheInternet 110 may include a global system of interconnected computernetworks and devices that use common communication protocols, such asthe transmission control protocol (TCP), user datagram protocol (UDP)and the internet protocol (IP) in the TCP/IP internet protocol suite.The networks 112 may include wired or wireless communications networksowned and/or operated by other service providers. For example, thenetworks 112 may include another core network connected to one or moreRANs, which may employ the same RAT as the RAN 103/104/105 or adifferent RAT.

Some or all of the WTRUs 102 a, 102 b, 102 c, 102 d in thecommunications system 100 may include multi-mode capabilities, i.e., theWTRUs 102 a, 102 b, 102 c, 102 d may include multiple transceivers forcommunicating with different wireless networks over different wirelesslinks. For example, the WTRU 102 c shown in FIG. 1A may be configured tocommunicate with the base station 114 a, which may employ acellular-based radio technology, and with the base station 114 b, whichmay employ an IEEE 802 radio technology.

FIG. 1B is a system diagram of an example WTRU 102. As shown in FIG. 1B,the WTRUs 102 a, 102 b, 102 c, 102 d may include a processor 118, atransceiver 120, a transmit/receive element 122, a speaker/microphone124, a keypad 126, a display/touchpad 128, non-removable memory 130,removable memory 132, a power source 134, a global positioning system(GPS) chipset 136, and other peripherals 138. It will be appreciatedthat the WTRU 102 may include any sub-combination of the foregoingelements while remaining consistent with an embodiment.

The processor 118 of the WTRU 102 may be a general purpose processor, aspecial purpose processor, a conventional processor, a digital signalprocessor (DSP), a plurality of microprocessors, one or moremicroprocessors in association with a DSP core, a controller, amicrocontroller, Application Specific Integrated Circuits (ASICs), FieldProgrammable Gate Array (FPGAs) circuits, any other type of integratedcircuit (IC), a state machine, and the like. The processor 118 mayperform signal coding, data processing, power control, input/outputprocessing, and/or any other functionality that enables the WTRU 102 tooperate in a wireless environment. The processor 118 may be coupled tothe transceiver 120, which may be coupled to the transmit/receiveelement 122. While FIG. 1B depicts the processor 118 and the transceiver120 as separate components, it will be appreciated that the processor118 and the transceiver 120 may be integrated together in an electronicpackage or chip.

The transmit/receive element 122 of the WTRU 102 may be configured totransmit signals to, or receive signals from, a base station (e.g., thebase station 114 a) over the air interface 115/116/117. For example, inone embodiment, the transmit/receive element 122 may be an antennaconfigured to transmit and/or receive RF signals. In another embodiment,the transmit/receive element 122 may be an emitter/detector configuredto transmit and/or receive IR, UV, or visible light signals, forexample. In yet another embodiment, the transmit/receive element 122 maybe configured to transmit and receive both RF and light signals. It willbe appreciated that the transmit/receive element 122 may be configuredto transmit and/or receive any combination of wireless signals.

In addition, although the transmit/receive element 122 is depicted inFIG. 1B as a single element, the WTRU 102 may include any number oftransmit/receive elements 122. More specifically, the WTRU 102 mayemploy MIMO technology. Thus, in one embodiment, the WTRU 102 mayinclude two or more transmit/receive elements 122 (e.g., multipleantennas) for transmitting and receiving wireless signals over the airinterface 115/116/117.

The transceiver 120 of the WTRU 102 may be configured to modulate thesignals that are to be transmitted by the transmit/receive element 122and to demodulate the signals that are received by the transmit/receiveelement 122. As noted above, the WTRU 102 may have multi-modecapabilities. Thus, the transceiver 120 may include multipletransceivers for enabling the WTRU 102 to communicate via multiple RATs,such as UTRA and IEEE 802.11, for example.

The processor 118 of the WTRU 102 may be coupled to, and may receiveuser input data from, the speaker/microphone 124, the keypad 126, and/orthe display/touchpad (e.g., a liquid crystal display (LCD) display unitor organic light-emitting diode (OLED) display unit). The processor 118may also output user data to the speaker/microphone 124, the keypad 126,and/or the display/touchpad 128. In addition, the processor 118 mayaccess information from, and store data in, any type of suitable memory,such as the non-removable memory 130 and/or the removable memory 132.The non-removable memory 130 may include random-access memory (RAM),read-only memory (ROM), a hard disk, or any other type of memory storagedevice. The removable memory 132 may include a subscriber identitymodule (SIM) card, a memory stick, a secure digital (SD) memory card,and the like. In other embodiments, the processor 118 may accessinformation from, and store data in, memory that is not physicallylocated on the WTRU 102, such as on a server or a home computer.

The processor 118 may receive power from the power source 134, and maybe configured to distribute and/or control the power to the othercomponents in the WTRU 102. The power source 134 may be any suitabledevice for powering the WTRU 102. For example, the power source 134 mayinclude one or more dry cell batteries (e.g., nickel-cadmium (NiCd),nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion),etc.), solar cells, fuel cells, and the like.

The processor 118 may also be coupled to the GPS chipset 136, which maybe configured to provide location information (e.g., longitude andlatitude) regarding the current location of the WTRU 102. In additionto, or in lieu of, the information from the GPS chipset 136, the WTRU102 may receive location information over the air interface 115/116/117from a base station (e.g., base stations 114 a, 114 b) and/or determineits location based on the timing of the signals being received from twoor more nearby base stations. It will be appreciated that the WTRU 102may acquire location information by way of any suitablelocation-determination method while remaining consistent with anembodiment.

The processor 118 may further be coupled to other peripherals 138, whichmay include one or more software and/or hardware modules that provideadditional features, functionality and/or wired or wirelessconnectivity. For example, the peripherals 138 may include anaccelerometer, an e-compass, a satellite transceiver, a digital camera(for photographs or video), a universal serial bus (USB) port, avibration device, a television transceiver, a hands free headset, aBluetooth® module, a frequency modulated (FM) radio unit, a digitalmusic player, a media player, a video game player module, an Internetbrowser, and the like.

FIG. 1C is a system diagram of the RAN 103 and the core network 106according to an embodiment. As noted above, the RAN 103 may employ aUTRA radio technology to communicate with the WTRUs 102 a, 102 b, 102 cover the air interface 115. The RAN 103 may also be in communicationwith the core network 106. As shown in FIG. 1C, the RAN 103 may includeNode-Bs 140 a, 140 b, 140 c, which may each include one or moretransceivers for communicating with the WTRUs 102 a, 102 b, 102 c overthe air interface 115. The Node-Bs 140 a, 140 b, 140 c may each beassociated with a particular cell (not shown) within the RAN 103. TheRAN 103 may also include RNCs 142 a, 142 b. It will be appreciated thatthe RAN 103 may include any number of Node-Bs and RNCs while remainingconsistent with an embodiment.

As shown in FIG. 1C, the Node-Bs 140 a, 140 b may be in communicationwith the RNC 142 a. Additionally, the Node-B 140 c may be incommunication with the RNC 142 b. The Node-Bs 140 a, 140 b, 140 c maycommunicate with the respective RNCs 142 a, 142 b via an Iub interface.The RNCs 142 a, 142 b may be in communication with one another via anIur interface. Each of the RNCs 142 a, 142 b may be configured tocontrol the respective Node-Bs 140 a, 140 b, 140 c to which it isconnected. In addition, each of the RNCs 142 a, 142 b may be configuredto carry out or support other functionality, such as outer loop powercontrol, load control, admission control, packet scheduling, handovercontrol, macrodiversity, security functions, data encryption, and thelike.

The core network 106 shown in FIG. 1C may include a media gateway (MGW)144, a mobile switching center (MSC) 146, a serving GPRS support node(SGSN) 148, and/or a gateway GPRS support node (GGSN) 150. While each ofthe foregoing elements are depicted as part of the core network 106, itwill be appreciated that any one of these elements may be owned and/oroperated by an entity other than the core network operator.

The RNC 142 a in the RAN 103 may be connected to the MSC 146 in the corenetwork 106 via an IuCS interface. The MSC 146 may be connected to theMGW 144. The MSC 146 and the MGW 144 may provide the WTRUs 102 a, 102 b,102 c with access to circuit-switched networks, such as the PSTN 108, tofacilitate communications between the WTRUs 102 a, 102 b, 102 c andtraditional land-line communications devices.

The RNC 142 a in the RAN 103 may also be connected to the SGSN 148 inthe core network 106 via an IuPS interface. The SGSN 148 may beconnected to the GGSN 150. The SGSN 148 and the GGSN 150 may provide theWTRUs 102 a, 102 b, 102 c with access to packet-switched networks, suchas the Internet 110, to facilitate communications between and the WTRUs102 a, 102 b, 102 c and IP-enabled devices.

As noted above, the core network 106 may also be connected to thenetworks 112, which may include other wired or wireless networks thatare owned and/or operated by other service providers.

FIG. 1D is a system diagram of the RAN 104 and the core network 107according to an embodiment. As noted above, the RAN 104 may employ anE-UTRA radio technology to communicate with the WTRUs 102 a, 102 b, 102c over the air interface 116. The RAN 104 may also be in communicationwith the core network 107.

The RAN 104 may include eNode-Bs 160 a, 160 b, 160 c, though it will beappreciated that the RAN 104 may include any number of eNode-Bs whileremaining consistent with an embodiment. The eNode-Bs 160 a, 160 b, 160c may each include one or more transceivers for communicating with theWTRUs 102 a, 102 b, 102 c over the air interface 116. In one embodiment,the eNode-Bs 160 a, 160 b, 160 c may implement MIMO technology. Thus,the eNode-B 160 a, for example, may use multiple antennas to transmitwireless signals to, and receive wireless signals from, the WTRU 102 a.

Each of the eNode-Bs 160 a, 160 b, 160 c may be associated with aparticular cell (not shown) and may be configured to handle radioresource management decisions, handover decisions, scheduling of usersin the uplink and/or downlink, and the like. As shown in FIG. 1D, theeNode-Bs 160 a, 160 b, 160 c may communicate with one another over an X2interface.

The core network 107 shown in FIG. 1D may include a mobility managementgateway (MME) 162, a serving gateway 164, and a packet data network(PDN) gateway 166. While each of the foregoing elements are depicted aspart of the core network 107, it will be appreciated that any one ofthese elements may be owned and/or operated by an entity other than thecore network operator.

The MME 162 may be connected to each of the eNode-Bs 160 a, 160 b, 160 cin the RAN 104 via an S1 interface and may serve as a control node. Forexample, the MME 162 may be responsible for authenticating users of theWTRUs 102 a, 102 b, 102 c, bearer activation/deactivation, selecting aparticular serving gateway during an initial attach of the WTRUs 102 a,102 b, 102 c, and the like. The MME 162 may also provide a control planefunction for switching between the RAN 104 and other RANs (not shown)that employ other radio technologies, such as GSM or WCDMA.

The serving gateway 164 may be connected to each of the eNode-Bs 160 a,160 b, 160 c in the RAN 104 via the S1 interface. The serving gateway164 may generally route and forward user data packets to/from the WTRUs102 a, 102 b, 102 c. The serving gateway 164 may also perform otherfunctions, such as anchoring user planes during inter-eNode B handovers,triggering paging when downlink data is available for the WTRUs 102 a,102 b, 102 c, managing and storing contexts of the WTRUs 102 a, 102 b,102 c, and the like.

The serving gateway 164 may also be connected to the PDN gateway 166,which may provide the WTRUs 102 a, 102 b, 102 c with access topacket-switched networks, such as the Internet 110, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and IP-enableddevices.

The core network 107 may facilitate communications with other networks.For example, the core network 107 may provide the WTRUs 102 a, 102 b,102 c with access to circuit-switched networks, such as the PSTN 108, tofacilitate communications between the WTRUs 102 a, 102 b, 102 c andtraditional land-line communications devices. For example, the corenetwork 107 may include, or may communicate with, an IP gateway (e.g.,an IP multimedia subsystem (IMS) server) that serves as an interfacebetween the core network 107 and the PSTN 108. In addition, the corenetwork 107 may provide the WTRUs 102 a, 102 b, 102 c with access to thenetworks 112, which may include other wired or wireless networks thatare owned and/or operated by other service providers.

FIG. 1E is a system diagram of the RAN 105 and the core network 109according to an embodiment. The RAN 105 may be an access service network(ASN) that employs IEEE 802.16 radio technology to communicate with theWTRUs 102 a, 102 b, 102 c over the air interface 117. As will be furtherdiscussed below, the communication links between the differentfunctional entities of the WTRUs 102 a, 102 b, 102 c, the RAN 105, andthe core network 109 may be defined as reference points.

As shown in FIG. 1E, the RAN 105 may include base stations 180 a, 180 b,180 c, and an ASN gateway 182, though it will be appreciated that theRAN 105 may include any number of base stations and ASN gateways whileremaining consistent with an embodiment. The base stations 180 a, 180 b,180 c may each be associated with a particular cell (not shown) in theRAN 105 and may each include one or more transceivers for communicatingwith the WTRUs 102 a, 102 b, 102 c over the air interface 117. In oneembodiment, the base stations 180 a, 180 b, 180 c may implement MIMOtechnology. Thus, the base station 180 a, for example, may use multipleantennas to transmit wireless signals to, and receive wireless signalsfrom, the WTRU 102 a. The base stations 180 a, 180 b, 180 c may alsoprovide mobility management functions, such as handoff triggering,tunnel establishment, radio resource management, traffic classification,quality of service (QoS) policy enforcement, and the like. The ASNgateway 182 may serve as a traffic aggregation point and may beresponsible for paging, caching of subscriber profiles, routing to thecore network 109, and the like.

The air interface 117 between the WTRUs 102 a, 102 b, 102 c and the RAN105 may be defined as an R1 reference point that implements the IEEE802.16 specification. In addition, each of the WTRUs 102 a, 102 b, 102 cmay establish a logical interface (not shown) with the core network 109.The logical interface between the WTRUs 102 a, 102 b, 102 c and the corenetwork 109 may be defined as an R2 reference point, which may be usedfor authentication, authorization, IP host configuration management,and/or mobility management.

The communication link between each of the base stations 180 a, 180 b,180 c may be defined as an R8 reference point that includes protocolsfor facilitating WTRU handovers and the transfer of data between basestations. The communication link between the base stations 180 a, 180 b,180 c and the ASN gateway 182 may be defined as an R6 reference point.The R6 reference point may include protocols for facilitating mobilitymanagement based on mobility events associated with each of the WTRUs102 a, 102 b, 102 c.

As shown in FIG. 1E, the RAN 105 may be connected to the core network109. The communication link between the RAN 105 and the core network 109may defined as an R3 reference point that includes protocols forfacilitating data transfer and mobility management capabilities, forexample. The core network 109 may include a mobile IP home agent(MIP-HA) 184, an authentication, authorization, accounting (AAA) server186, and a gateway 188. While each of the foregoing elements aredepicted as part of the core network 109, it will be appreciated thatany one of these elements may be owned and/or operated by an entityother than the core network operator.

The MIP-HA may be responsible for IP address management, and may enablethe WTRUs 102 a, 102 b, 102 c to roam between different ASNs and/ordifferent core networks. The MIP-HA 184 may provide the WTRUs 102 a, 102b, 102 c with access to packet-switched networks, such as the Internet110, to facilitate communications between the WTRUs 102 a, 102 b, 102 cand IP-enabled devices. The AAA server 186 may be responsible for userauthentication and for supporting user services. The gateway 188 mayfacilitate interworking with other networks. For example, the gateway188 may provide the WTRUs 102 a, 102 b, 102 c with access tocircuit-switched networks, such as the PSTN 108, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and traditionalland-line communications devices. In addition, the gateway 188 mayprovide the WTRUs 102 a, 102 b, 102 c with access to the networks 112,which may include other wired or wireless networks that are owned and/oroperated by other service providers.

Although not shown in FIG. 1E, it will be appreciated that the RAN 105may be connected to other ASNs and the core network 109 may be connectedto other core networks. The communication link between the RAN 105 theother ASNs may be defined as an R4 reference point, which may includeprotocols for coordinating the mobility of the WTRUs 102 a, 102 b, 102 cbetween the RAN 105 and the other ASNs. The communication link betweenthe core network 109 and the other core networks may be defined as an R5reference, which may include protocols for facilitating interworkingbetween home core networks and visited core networks.

The example communication system described herein may support an airinterface with which one or more of the following may be enabled:improved broadband performance (IBB), industrial control andcommunications (ICC) and vehicular applications (V2X), and massivemachine-type communications (mMTC). The air interface may supportultra-low latency communications (LLC), ultra-reliable communications(URC), and/or MTC operations (e.g., including narrow band operations).With respect to LLC, one or more of the following may be supported: alow air interface latency (e.g., 1 ms RTT), a short TTI (e.g., between100 us and 250 us), an ultra-low access latency (e.g., access latencymay be associated with an amount of time from an initial system accessto the completion of transmission of a first user plane data unit),and/or a low end-to-end (e2e) latency (e.g., less than 10 ms, e.g., inICC and/or V2X). With respect to URC, transmission/communicationreliability may approach, for example, 99.999% transmission successand/or service availability. Mobility for speed in the range of 0-500km/hour may be desired. Packet loss ratio may be designed to be lessthan 10e⁻⁶ (e.g., in ICC and V2X). With respect to MTC operation, theair interface may support narrowband operations (e.g., using less than200 KHz), extended battery life (e.g., up to 15 years of autonomy),and/or reduced communication overhead (e.g., at least for small and/orinfrequent data transmissions such as those with a data rate in therange of 1-100 kbps and/or with an access latency of seconds to hours).

The example communication system described herein may utilize OFDM as awaveform (e.g., at least in the downlink). OFDM may be a basic signalformat for data transmissions in LTE and/or IEEE 802.11. With OFDM, aspectrum may be divided into multiple parallel orthogonal subbands. Asubcarrier may be shaped using a rectangular window in the time domain,which may lead to sinc-shaped subcarriers in the frequency domain. OFDMAmay be designed to attempt to achieve high levels of frequencysynchronization and/or uplink timing alignment within the duration of acyclic prefix (e.g., to maintain orthogonality between signals and/or tominimize inter-carrier interference). The synchronization requirementsof OFDM (e.g., conventional OFDM or CP-OFDM) may be challenging to meetin the example communication system designed to achieve the other designgoals mention above (e.g., because a WTRU may be connected to multipleaccess points simultaneously). Additional power reduction may be appliedto uplink transmissions to comply with spectral emission requirements toadjacent bands (e.g., in the presence of aggregation of fragmentedspectrum for the WTRU's transmissions). In light of these challenges,the example communication system described herein may impose morestringent RF requirements for CP-OFDM (e.g., when a large amount ofcontiguous spectrum is used that does not rely on aggregation). If used,an CP-OFDM-based transmission scheme may lead to a downlink physicallayer similar to that of a legacy system (e.g., with modifications topilot signal density and location).

The example communication system described herein may utilize otherwaveforms. For example, a downlink transmission scheme in the examplecommunication system may be based on a multicarrier (MC) waveform. TheMC waveform may be characterized, for example, by high spectralcontainment (e.g., lower side lobes and/or lower OOB emissions). The MCwaveform may divide a channel into subchannels and modulate data symbolson subcarriers in these subchannels. An example MC waveform isOFDM-OQAM. With OFDM-OQAM, a filter may be applied in the time domain(e.g., per subcarrier) to the OFDM signal, for example, to reduce OOB.OFDM-OQAM may cause low interference to adjacent bands, may not needlarge guard bands, and may not utilize a cyclic prefix. OFDM-OQAM may bea suitable FBMC technique. It should be noted, however, that in someexample systems OFDM-OQAM may be sensitive to multipath effects and tohigh delay spread in terms of orthogonality. Equalization and channelestimation with OFDM-OQAM may be complicated.

Another example MC waveform that may be used is UFMC (UF-OFDM). WithUFMC (UF-OFDM), a filter may be applied in the time domain to an OFDMsignal (e.g., to reduce OOB). In an example, filtering may be appliedper subband so that spectrum fragments may be used (e.g., to reduceimplementation complexity). If some spectrum fragments in the band areunused, OOB emissions in these fragments may remain high (e.g., as maybe the case for conventional OFDM). For at least this reason, UF-OFDMmay be a suitable waveform to use at least at the edges of the filteredspectrum.

It should be noted that the waveforms described herein are examples andtherefore not the only waveforms with which the embodiments describedherein may be implemented. The example waveforms may make multiplexingpossible in at least signals with non-orthogonal characteristics (e.g.,such as signals with different subcarrier spacing). The examplewaveforms may allow co-existence of asynchronous signals (e.g., withoutrequiring complex interference cancellation receivers). The examplewaveforms may facilitate the aggregation of fragmented spectrum inbaseband processing, for example, as a lower cost alternative toaggregating the fragmented spectrum as part of RF processing.

In the example communication system, there may be co-existence ofdifferent waveforms within the same band (e.g., at least to support mMTCnarrowband operation that may use SCMA). A combination of differentwaveforms, such as CP-OFDM, OFDM-OQAM and/or UF-OFDM, for some or allaspects of operation and/or for either or both of downlink and uplinktransmissions, may be supported. The co-existence of waveforms mayinclude, for example, transmissions using different types of waveformsbetween different WTRUs or transmissions from the same WTRU (e.g., thetransmissions may be simultaneous, with some overlap, or consecutive inthe time domain).

Other co-existence aspects may include, for example, support for hybridtypes of waveforms (e.g., waveforms and/or transmissions that support atleast a possibly varying CP duration such as one that varies from onetransmission to another), support for a combination of a CP and a lowpower tail (e.g., a zero tail), support for a form of hybrid guardinterval (e.g., using a low power CP and/or an adaptive low power tail),and/or the like. The example waveforms may support dynamic variationand/or control of one or more other aspects such as filtering. Forinstance, one or more of the following may be dynamically varied and/orcontrolled: whether to apply filtering at the edge of the spectrum usedfor receiving transmissions of a given carrier frequency, whether toapply filtering at the edge of a spectrum used for receivingtransmissions associated with a specific SOM, whether to apply filteringper subband or per group, and/or the like. In general, a waveform/typeof waveform may be considered an example of a transmission parameterthat may be varied in order to achieve different types of transmissionschemes. Thus, a first transmission scheme may utilize a first type ofwaveform (e.g., CP-OFDM) while a second transmission scheme may utilizea different waveform (e.g., OFDM-OQAM). The different waveforms may beassociated with different transmission characteristics such as differentpotential throughputs, different latency characters, different overheadrequirements, etc.

An uplink transmission scheme may use the same waveform or a differentwaveform as in a downlink transmission scheme. Multiplexing oftransmissions to and from different WTRUs in the same cell may be basedon FDMA and/or TDMA.

The design of the example communication system described herein may becharacterized by a high degree of spectrum flexibility. Such spectrumflexibility may allow (e.g., enable) deployment in different frequencybands with different characteristics, including, for example, differentduplex arrangements and/or different sizes of available spectrums (e.g.,including contiguous and non-contiguous spectrum allocations in the sameband or different bands). The spectrum flexibility may support variabletiming aspects including, for example, support for multiple TTI lengthsand/or support for asynchronous transmissions.

The example communication system described herein may be characterizedby flexibility in duplexing arrangements. For example, the examplecommunication system may support both TDD and FDD duplexing schemes. ForFDD operations, supplemental downlink operations may be supported usingspectrum aggregation. Both full-duplex FDD and half-duplex FDDoperations may be supported. For TDD operations, DL/UL allocation may bedynamic. For instance, the allocation may not be based on a fixed DL/ULframe configuration; rather, the length of a DL or UL transmissioninterval may be set per transmission opportunity.

The example communication system described herein may be characterizedby flexibility in bandwidth allocation. For example, differenttransmission bandwidths may be enabled on uplink and/or downlinktransmissions (e.g., the transmission bandwidth may range from a nominalsystem bandwidth to a maximum bandwidth corresponding to a systembandwidth). In an example single carrier operation, supported systembandwidths may include, for example, at least 5, 10, 20, 40 and 80 MHz.In an example, supported system bandwidths may be any bandwidth within agiven range (e.g., from a few MHz up to 160 MHz). Nominal bandwidths mayhave one or more values (e.g., one or more fixed values). Narrowbandtransmissions of up to 200 KHz may be supported (e.g., which may bewithin the operating bandwidth of MTC devices).

FIG. 2 illustrates example transmission bandwidths that may be supportedby the example communication system. The system bandwidth referred toherein may be associated with the largest portion of the spectrum thatmay be managed by a given carrier network. For such a carrier, theportion of the spectrum that a WTRU may support (e.g., minimallysupport) for cell acquisition, measurements and initial access to thenetwork may correspond to a nominal system bandwidth. The WTRU may beconfigured with a channel bandwidth that is within the range of theentire system bandwidth. The WTRU's configured channel bandwidth may ormay not include the nominal portion of the system bandwidth.

One example reason that bandwidth flexibility may be achieved in theexample communication system described herein is that some or all of theapplicable RF requirements for a given operating bandwidth (e.g., amaximum operating bandwidth) may be met without introducing additionalallowed channel bandwidths for that operating band. This may be due to,for example, efficient support of baseband filtering of the relevantfrequency domain waveform. The embodiments described herein may utilizetechniques for configuring, reconfiguring and/or dynamically changing aWTRU's channel bandwidth for single carrier operations. The embodimentsdescribed herein may allocate spectrum for narrowband transmissionswithin the nominal system bandwidth, a system bandwidth or a configuredchannel bandwidth. A physical layer of the example communication systemmay be band-agnostic. The physical layer may support operations in alicensed band (e.g., below 5 GHz) as well as operations in an unlicensedband (e.g., in the range of 5-6 GHz or higher). For operations in theunlicensed band, a LBT Cat 4-based channel access framework (e.g., achannel access framework similar to LTE LAA) may be supported. Theembodiments described herein may utilize techniques for scaling and/ormanaging cell-specific and/or WTRU-specific channel bandwidths fordifferent spectrum block sizes. These techniques may be associated with,for example, scheduling, addressing resources, broadcasting signals,measuring, etc. Spectrum block sizes may be arbitrary.

The example communication system described herein may be characterizedby flexibility in spectrum allocation. Downlink control channels andsignals may support FDM operations. A WTRU may acquire a downlinkcarrier, e.g., by receiving transmissions via the nominal part (e.g.,only the nominal part) of the system bandwidth. For instance, the WTRUmay not initially be configured to receive transmissions over the entirebandwidth managed by the concerned carrier network.

Downlink data channels may be allocated over a bandwidth that may or maynot correspond to the nominal system bandwidth. The allocation may bewithout restrictions, e.g., other than being within a WTRU's configuredchannel bandwidth. For example, a carrier may be operated with a 12 MHzsystem bandwidth using a 5 MHz nominal bandwidth. Such an arrangementmay allow devices supporting 5 MHz maximum RF bandwidth to acquire andaccess the system, while allocating +10 to −10 MHz of the carrierfrequency to other WTRUs that support up to 20 MHz worth of channelbandwidth.

FIG. 3 shows an example of spectrum allocation where differentsubcarriers may be assigned (e.g., at least conceptually) to differentSOMs. The different SOMs may be used to meet different requirements fordifferent transmissions. A SOM may include/be defined based on one ormore of a subcarrier spacing, a TTI length, or a reliability aspect(e.g., such as a HARQ processing aspect). A SOM may comprise a secondarycontrol channel. For example, a SOM may include a separate controlchannel (e.g., separate from a primary control channel) that anassociated WTRU may be configured to monitor. A SOM may be used to referto a specific waveform or may be related to a processing aspect, e.g.,to support co-existence of different waveforms in the same carrier usingFDM and/or TDM, or co-existence of FDD and TDD (e.g., perform FDDoperations in a TDD band, e.g., such as in a TDM manner).

A WTRU may be configured to perform transmissions according to one ormore SOMs. For example, a SOM may correspond to transmissions that useone or more of the following: a specific TTI duration, a specificinitial power level, a specific HARQ processing type, a specific upperbound for successful HARQ reception/transmission, a specifictransmission mode, a specific physical channel (uplink or downlink), aspecific waveform type, or a transmission according to a specific RAT(e.g., which may use legacy LTE or 5G transmission techniques). A SOMmay correspond to a QoS level and/or related aspects such asmaximum/target latency, maximum/target BLER, and/or the like. A SOM maycorrespond to a spectrum area and/or to a specific control channel oraspects thereof (e.g., search space, DCI type, etc.). For example, aWTRU may be configured with a SOM for one or more of a URC type ofservice, a LLC type of service, or a MBB type of service. A WTRU mayhave (e.g., the WTRU may receive) a configuration for a SOM for systemaccess and/or for transmission/reception of L3 control signaling (e.g.,RRC). For example, the WTRU may be configured to send and/or receive L3control signaling using a portion of a system spectrum such as thenominal system bandwidth, as described herein.

Resources of a given SOM may be defined or described in terms of aspecific numerology for that SOM. For example, a first SOM may use afirst numerology (e.g., a first subcarrier spacing, a first symbollength, a first TTI length, a first bandwidth, a first waveform type,etc.) and a second first SOM may use a second numerology (e.g., a secondsubcarrier spacing, a second symbol length, a second TTI length, asecond bandwidth, a second waveform type, etc.). The terms SOM andnumerology may be referred to interchangeably herein.

A WTRU in the example communication system described herein may beconfigured to switch to a different transmission scheme if the WTRUdetermines that it is unable to successfully complete a transmissionusing an original transmission scheme. A transmission scheme, asdescribed herein, may encompass resources, transmission techniques,transmission parameters, and/or other operational aspects associatedwith the performance of a transmission. For example, differenttransmission schemes may utilize different SOMs and/or differentnumerologies. As such, SOMs and/or numerologies may be an example of anoperational aspect that may be varied for different types oftransmission schemes.

The example communication system described herein may support spectrumaggregation (e.g., for at least single carrier operations). For example,spectrum aggregation may be supported in situations where a WTRU iscapable of transmitting and/or receiving multiple transport blocks overcontiguous and/or non-contiguous sets of physical resource blocks (PRBs)within a same operating band. A transport block may be mapped toseparate sets of PRBs. Transmissions associated with different SOMs maybe performed simultaneously.

The example communication system described herein may supportmulticarrier operations. Such support may be provided, for example, byutilizing contiguous and/or non-contiguous spectrum blocks within a sameoperating band or across two or more operating bands. The examplecommunication system may support aggregation of spectrum blocks. Forexample, spectrum blocks may be aggregated using different modes such asFDD and/or TDD, and/or different channel access techniques such aslicensed and unlicensed band operation below 6 GHz. A WTRU'smulticarrier aggregation operation may be configured, reconfigured,and/or dynamically changed by the network and/or the WTRU.

Downlink and/or uplink transmissions may be organized into radio frames.The radio frames may be characterized by a number of fixed aspects(e.g., location of downlink control information) and/or a number ofvarying aspects (e.g., transmission timing and/or supported types oftransmissions). A basic time interval (BTI) may be expressed in terms ofa number (e.g., an integer number) of one or more symbol(s). A symbolduration may be a function of the subcarrier spacing applicable to atime-frequency resource. For at least FDD, subcarrier spacing may differbetween an uplink carrier frequency f_(UL) and a downlink carrierfrequency f_(DL) for a given frame. A transmission time interval (TTI)may be the minimum time supported by the system between consecutivetransmissions. One or more (e.g., each) of the consecutive transmissionsmay be associated with different transport blocks (TBs) for the downlink(TTIDL) and/or the uplink (UL TRx). A preamble of the downlink and/oruplink (if applicable) may be excluded from TTI determination. Controlinformation (e.g., DCI for downlink or UCI for uplink) may be includedin TTI determination. A TTI may be expressed in terms of a number of(e.g., an integer number of) one of more BTI(s). A BTI may be specificand/or may be associated with a given SOM and/or numerology.

The example communication system described herein may support variousframe durations, including, for example, 100 us, 125 us (⅛ ms), 142.85us (e.g., 1/7 ms or 2 nCP LTE OFDM symbols), and/or 1 ms. Framedurations may be set to enable alignment with a legacy LTE timingstructure. A frame may start with downlink control information (DCI) ofa fixed time duration t_(dci), that precedes downlink data transmission(DL TRx) for the concerned carrier frequency (e.g., f_(UL+DL) for TDDand f_(DL) for FDD). For TDD duplexing (e.g., only for TDD duplexing), aframe may comprise a downlink portion (e.g., DCI and/or DL TRx) and/oran uplink portion (e.g., UL TRx). A switching gap (“swg”) may precede(e.g., always precede) the uplink portion of the frame, if present. ForFDD duplexing (e.g., only for FDD duplexing), a frame may comprise adownlink reference TTI and one or more TTI(s) for the uplink. The startof an uplink TTI may be derived using an offset (t_(offset)) appliedfrom the start of the downlink reference frame, which may overlap withthe start of the uplink frame. Duplexing modes (e.g., TDD versus FDD)may be an example of an operational aspect that may be varied fordifferent types of transmission schemes.

The example communication system described herein may supportD2DN2x/Sidelink operation in a frame. The example communication systemmay utilize various configurations/techniques to provide theD2D/V2x/Sidelink support. In an example (e.g., when TDD is used), theexample communication system may include respective downlink control andforward direction transmissions in the DCI+DL TRx portion of a frame(e.g., when a semi-static allocation of resources is used), or in the DLTRx portion of a frame (e.g., when a dynamic allocation of resources isused). Additionally or alternatively, the example communication systemmay include respective reverse direction transmissions in the UL TRxportion of a frame. In an example (e.g., when FDD is used), the examplecommunication system may support D2DN2x/Sidelink operations in the ULTRx portion of a frame, for example, by including respective downlinkcontrol, forward direction and reverse direction transmissions in the ULTRx portion of the frame. Further, resources associated with therespective transmissions may be dynamically allocated.

FIG. 4A shows an example TDD frame structure. FIG. 4B shows an exampleFDD frame structure.

The example communication system described herein may employ variousscheduling and/or rate control techniques, including, for example, ascheduling function in the MAC layer, a network-based scheduling mode,and/or a WTRU-based scheduling mode. A network-based scheduling mode mayresult in tight scheduling in terms of resources, timing and/ortransmission parameters of downlink transmissions and/or uplinktransmissions, for example. A WTRU-based scheduling mode may result inflexibility in terms of timing and/or transmission parameters, forexample. For one or more of the scheduling techniques (e.g., schedulingmodes), scheduling information may be valid for a single TTI or formultiple TTIs. Scheduling techniques (e.g., scheduling modes) may be anexample of an operational aspect that may be varied for different typesof transmission schemes.

Network-based scheduling may enable a network to tightly manage radioresources assigned to different WTRUs (e.g., so as to optimize thesharing of such resources). In at least some cases, the network mayconduct the scheduling dynamically. WTRU-based scheduling may enable aWTRU to access (e.g., opportunistically access) uplink resources withminimal latency on a per-need basis and/or within a set of shared ordedicated uplink resources assigned by the network. The shared ordedicated uplink resources may be assigned dynamically or statically. AWTRU may be configured to perform synchronized and/or unsynchronizedopportunistic transmissions. A WTRU may be configured to performcontention-based and/or contention-free transmissions. For example, aWTRU may be configured to perform opportunistic transmissions (e.g.,scheduled or unscheduled) to meet ultra-low latency requirements (e.g.,for 5G) and/or power saving requirements (e.g., in mMTC use cases).

The example communication system described herein may prioritize logicalchannels. For example, the example communication system may beconfigured to associate data and resources (e.g., for uplinktransmissions). The example communication system may multiplex data thathave different QoS requirements within a same transport block if, forexample, such multiplexing does not negatively impact the QoSrequirements of a service or unnecessarily waste system resources.Logical channel prioritization may be an example of an operationalaspect that may be varied for different types of transmission schemes.

The example communication system described herein may encode atransmission using different encoding techniques. Different encodingtechniques may have different characteristics. An encoding technique maygenerate a sequence of one or more information units or blocks. Aninformation unit or block (e.g., each information unit or block) may beself-contained. For example, an error in the transmission of a firstblock may not impair the ability of the receiver to successfully decodea second block if, for example, the second block is error-free, and/orif sufficient redundancy can be found in the second block or in adifferent block for which at least a portion was successfully decoded.

Example encoding techniques may include raptor/fountain codes whereby atransmission may comprise a sequence of N raptor codes. One or more suchcodes may be mapped to one or more transmission symbols in time. Atransmission symbol may correspond to one or more sets of informationbits (e.g., one or more octets). Using such an encoding technique, FECmay be added to a transmission whereby the transmission may use N+1 orN+2 raptor codes or symbols, assuming a one raptor code per symbolrelationship exists. This way, transmissions may be resilient to symbolloss, for example, due to interference and/or puncturing by anothertransmission that is overlapping in time. Encoding/decoding techniquesmay be an example of an operational aspect that may be varied fordifferent types of transmission schemes.

A WTRU may be configured to receive and/or detect one or more systemsignatures. A system signature may comprise a signal structure using asequence. The signal may be similar to a synchronization signal. Thesystem signature may be specific to a particular node or TRP within agiven area (e.g., may uniquely identify the node or TRP), or it may becommon to a plurality of such nodes or TRPs within an area. One or moreof the foregoing aspects may not be known and/or may be irrelevant tothe WTRU. The WTRU may determine and/or detect a system signaturesequence, and may further determine one or more parameters associatedwith the system. For example, the WTRU may derive an index and use theindex to retrieve associated parameters (e.g., the WTRU may retrieve theparameters from a table such as an access table described herein). TheWTRU may use the received power associated with a system signature foropen-loop power control (e.g., to set an initial transmission power ifthe WTRU determines that it may access and/or transmit using applicableresources of the system). For example, the WTRU may use the timing ofthe received signature sequence to set the timing of a transmission(e.g., a preamble on a PRACH resource) if the WTRU determines that itmay access and/or transmit using applicable resources of the system.Different signal structures may be associated with different SOMs and/ordifferent numerologies. As such, signal structures may be an example ofan operational aspect that may be varied for different types oftransmission schemes.

A WTRU may be configured with a list of entries (e.g., operatingparameters) that may be referred to as an access table. Althoughreferred to as an access table, it should be noted that the list ofentries may be stored in any suitable type of structures including atable structure. The list of entries or access table may be indexed suchthat an entry (e.g., each entry) may be associated with a systemsignature and/or to a sequence thereof. The list or access table mayprovide initial access parameters for one or more areas. For example, anentry (e.g., each entry) in the list may provide one or more parametersassociated with performing an initial access to the system. Suchparameters may include, for example, one or more random accessparameters such as applicable physical layer resources (e.g., PRACHresources) in time and/or frequency, an initial power level, and/orphysical layer resources for response reception. Such parameters mayinclude access restrictions such as PLMN identity and/or CSGinformation. Such parameters may include routing-related informationsuch as an applicable routing area. An entry (e.g., each entry) may beassociated with and/or indexed by a system signature. An entry (e.g.,each entry) may be common to a plurality of nodes or TRPs. The WTRU mayreceive such a list or access table via a transmission over dedicatedresources (e.g., RRC configuration) and/or a transmission usingbroadcasted resources. In at least the latter case, the periodicity ofthe transmission of the access table may be long (e.g., up to 10240 ms).For example, the periodicity of the transmission of the access table maybe longer than the periodicity of the transmission of a signature (e.g.,which may be in the range of 100 ms). The access table described abovemay be an example of an operational aspect that may be varied fordifferent types of transmission schemes.

The example communication system described herein may support a varietyof use cases. Each use case may include a different set of QoSrequirements. There may be differentiation among these use cases interms of applicable radio resources and/or transmission techniques. Forexample, the use cases may be different in terms of TTI duration,reliability, diversity applied to the transmission, maximum latency,etc. QoS differentiation may be introduced for different data packets,data flows and/or data bearers (or their equivalents). Thedifferentiation may be in terms of maximum guaranteed delay budget,packet error rate, data rate, and/or the like. The MAC layer may handleone or more of the functionalities described herein in order to addressall or a subset of the following aspects.

Given different possible radio resources and/or transmission techniqueswith different characteristics, a WTRU may be configured to request,determine and/or access resources (e.g., suitable uplink transmissionresources) that support the QoS requirements of a data service. Givendifferent possible resource allocations (e.g., in the uplink and/ordownlink) with different characteristics, a WTRU may be configured toexercise control (e.g., to control grant and/or resource allocation)over downlink and uplink transmissions (e.g., determine and handle oneor more types of allocation differently). Given differentcharacteristics associated with different transport blocks, a WTRU maybe configured to multiplex and/or assemble MAC PDUs that meet theapplicable QoS requirements. For example, the WTRU may assign dataassociated with different bearers, different logical connections and/orthe like according to an extended set of rules (e.g., by taking intoconsideration the QoS properties of the concerned data and/or of the SOMassociated with the concerned TB). Given the use cases and transmissiontechniques described herein, a WTRU may be configured to satisfy one ormore pre-requisites for uplink transmissions (e.g., the pre-requisitesmay include UL TA, positioning, WTRU speed, PL estimate, etc.). Forexample, the WTRU may manage and/or determine whether it has sufficientpre-requisites for performing a given type of transmission.

The example communication system may perform scheduling and/orscheduling-related operations based on QoS requirements. A networkscheduler by itself may not always be able to enforce all types of QoSrequirements for all types of data. For example, a network-basedscheduling function may not have timely information and/or exactknowledge of the QoS requirements associated with data available foruplink transmission in a WTRU's buffer. A WTRU may be configured toenable services that have strict reliability and/or latency requirements(e.g., these behaviors may enable a WTRU to receive URLLC services). AWTRU may impact how/what data is transmitted (e.g., via additionalparameters). For example, a WTRU may be configured with one or moreparameters that are associated with a characterization of how data istransmitted. The characterization may represent constraints and/orrequirements that the WTRU is expected to meet and/or enforce whentransmitting data. Based on the characterization, the WTRU may performdifferent operations and/or adjust its behaviors, for example based on astate and/or characteristic of the data (e.g., as a function of thestate and/or characteristic of the data).

The example communication system described herein may include one ormore of the following time-related QoS requirements (e.g., time-relatedcharacteristics). These time-related QoS requirements may be helpful,for example, when a network scheduler is unable to enforcetiming/latency requirements by itself (e.g., for at least a subset ofthe data available for transmission). A WTRU may be configured totransmit data that are associated with one or more specific time-relatedQoS requirements. Depending on these time-related QoS requirements, aWTRU may change one or more operational aspects of a given transmissionscheme used for transmitting the data. For example, if the WTRU is nearthe end of a transmission using a first transmission scheme withoutsuccessfully transmitting the data (e.g., without meeting one or moretime-based QoS requirements), the WTRU may vary one or more operationalaspects of the first transmission scheme to switch to a secondtransmission scheme in order to try and successfully transmit the dataprior to expiry of the time-based QoS requirements.

The time-based QoS requirements described herein may include a maximumtime allowed for fulfilling one or more aspects of a data transmission(e.g., an uplink data transmission). A WTRU may determine whether such amaximum time is reached or exceeded based on observation and/orestimation. The time-based QoS requirements may include a maximum amountof time allowed for obtaining a suitable resource for the datatransmission. The WTRU may determine the time associated with theacquisition of a suitable resource by monitoring a control channel. Forexample, the WTRU may determine such time as a function of a grantreceived via the control channel, as a function of a parameter signaledin the control channel, and/or the like. The WTRU may determine a timeassociated with the acquisition of a suitable resource by monitoring aSOM associated with the resource acquisition. The WTRU may determine atime associated with the acquisition of a suitable resource bymonitoring one or more states of the WTRU. Such states may include, forexample, whether the WTRU is synchronized or unsynchronized, whether ascheduling request is ongoing, etc.

The time-based QoS requirements may include a maximum time that data isallowed to stay in a WTRU's transmission buffer. The WTRU may beconfigured to determine such a maximum time based on the timing of aninitial transmission of the data. For example, the WTRU may beconfigured to determine how long the data have been staying in theWTRU's transmission buffer by maintaining a timer that tracks the timeelapsed since the data entered the transmission buffer until thebeginning of an initial transmission of the data.

The time-based QoS requirements may include a maximum amount of time fora data transmission to reach a HARQ operational point. Using the x^(th)transmission of a PDU containing the relevant data as an example, thetime for a WTRU to reach a HARQ operational point may be determined asthe time it takes the WTRU to perform x^(th)−1 retransmissions of thePDU.

The time-based QoS requirements may include a maximum amount of timeallowed for successfully completing a data transmission or receivingfeedback on the transmission of a PDU containing the data. A WTRU maydetermine such time based on when the WTRU receives HARQ feedback suchas an HARQ ACK for a corresponding transport block.

The time-based QoS requirements may include a maximum value for aTime-To-Live (TTL) parameter associated with the data. Such a TTLparameter may be associated with, for example, a transmission of a datapacket or any other action taken by a WTRU with respect to the datapacket. For example, a WTRU may maintain (e.g., be configured with) aTTL parameter having a certain threshold value (e.g., N milliseconds) inassociation with the transmission of a data packet. The WTRU may monitora time lapse since the data packet became available for transmission(e.g., after the WTRU received the data packet in its buffer). If thethreshold is reached without the data packet being successfullytransmitted, the WTRU may determine that the TTL has expired. The WTRUmay perform different actions based on the amount of TTL remaining. Forexample, a WTRU may switch to a different transmission scheme upondetermining that the TTL has reached a threshold value.

The time-based QoS requirements may include a maximum amount of timeallowed for completing a logical grouping of data, for example based ona radio bearer. The time-based QoS requirements may include a maximumamount of time allowed for worst case or head-of-queue delays. A WTRUmay be configured to determine such delays based on data that spend thelongest time in the WTRU's buffer, for example.

The time-based QoS requirements may include an average or punctual timeassociated with one or more aspects of a data transmission. A WTRU maydetermine such an average or punctual time based on observation and/orestimation. For example, the time-based QoS requirements may include anaverage amount of time that data are allowed to stay in a WTRU'stransmission buffer (e.g., in association with the same logical channel,group and/or SOM). A WTRU may be configured to determine such an averagetime based on, for example, the time period between when the data becameavailable for transmission and when the data are transmitted. The WTRUmay determine the time at which such data became available fortransmission based on the timing for initiating a procedure to requestand/or acquire transmission resources, and/or the timing fortransmitting a signal to that effect. The WTRU may determine the time atwhich such data is transmitted based on, for example, the timing for aninitial transmission of the data, or the timing for receiving an ACK fora transmission of the data. The average described herein may be a movingaverage (e.g., within a window of a specific length), an average perburst associated with the data, an average since the WTRU last requestedresources for such data, or an average since the WTRU first acquiredresources for the transmission of such data.

The time-based QoS requirements may include a permissible variation froman average time. The variation may correspond to, for example, areduction or an increase to the average. Using the aforementioned buffertime as an example, the timing requirements may provide that the amountof time data are allowed to stay in the WTRU's transmission may exceedan average time only by a specific amount.

The time-based QoS requirements may include an average or punctual timeallowed for reducing data in the WTRU's buffer. For example, such anaverage or punctual time may be associated with reducing the amount ofdata in a WTRU's buffer to a certain level (e.g., the level may beconfigurable). The level may correspond to other time-relatedcharacteristics described herein, such as a maximum time allowed tosuccessfully complete a transmission. A WTRU may determine such anaverage time based on estimation or observation.

The time-based QoS requirements may include an average or punctual timefor worst case or head-of-queue delays. A WTRU may be configured todetermine such an average or punctual time based on multiple occurrencesof worse case delays.

The time-based QoS requirements may include an average or punctual timeallowed for performing logical grouping of data (e.g., based on a radiobearer and/or the like).

The time-based QoS requirements may be related to a HARQ entity, a HARQprocess type, and/or an ongoing HARQ process.

A WTRU may determine that the transmission of an uplink data unit (e.g.,an uplink data packet) has a QoS requirement. The QoS requirement may bea time-related QoS requirement associated with one or more aspects ofthe uplink transmission, as described herein. The WTRU may attempt totransmit the uplink data unit using a first transmission scheme. TheWTRU may determine whether the QoS requirement can be met using thefirst transmission scheme, for example for at least a subset of the dataavailable for transmission. For example, based on the QoS requirement,the WTRU may determine that a TTL parameter that the WTRU maintains forthe uplink data unit should not exceed a certain threshold. The TTLparameter may, for example, reflect an amount of time elapsed since theuplink data unit became available for transmission until the uplink dataunit is successfully transmitted. The WTRU may monitor the TTLparameter, and upon determining that the TTL has reached the thresholdbefore the uplink data unit can be successfully transmitted using thefirst transmission scheme, the WTRU may choose a second transmissionscheme to transmit the uplink data unit. The second transmission schememay differ from the first transmission scheme in at least oneoperational aspect, as described in greater detail herein.

The example communication system described herein may include one ormore of the following transmission rate-related requirements (e.g.,transmission-rate related characteristics). As described herein, anetwork scheduler may not always be able to enforce transmissionrate-related requirements by itself (e.g., for at least a subset of thedata available for transmission in a WTRU). A WTRU may be configuredsuch that the grouping of data may be associated with a transmissionrate-related requirement. Such grouping may include a logicalassociation between data packets and/or PDUs such as a LCH, a LCG, anassociation of data with SOMs and/or one or more aspect thereof, anassociation of data with a radio bearer, and/or the like. For example,the WTRU may be configured with a transmission rate (e.g., such as aprioritized bit rate) for such data. The WTRU may use the transmissionrate to determine how much data should be included in a transmission(e.g., by conducting a logical channel prioritization operation). Thetransmission rate-related requirements may be related to a HARQ entity,to a HARQ process type, and/or to an ongoing HARQ process. The WTRU mayobserve and/or estimate the rate of transmission for at least a subsetof the data (e.g., using similar metrics described herein for thetiming-related aspects). The WTRU may determine whether or not theconcerned transmission rate-related requirements may be met, and takedifferent actions based on determination (e.g., to switch to a differenttransmission scheme).

To illustrate, a WTRU may attempt to transmit an uplink data unit usinga first transmission scheme. The WTRU may determine whether or not atransmission rate-related requirement, or more generally a QoSrequirement associated with the uplink transmission, can be met (e.g.,for at least a subset of the data) using the first transmission scheme.If the WTRU determines that the transmission rate-related requirementmay not be met using the first transmission scheme, the WTRU maydetermine to switch to a second transmission scheme in order to satisfythe concerned transmission rate-related requirement. The secondtransmission scheme may differ from the first transmission scheme in atleast one operational aspect, as described in greater detail herein

The example communication system described herein may include one ormore of the following configuration-related requirements (e.g.,configuration-related characteristics). For example, a WTRU may beconfigured to give certain data a transmission priority (e.g., anabsolute priority) that supersedes one or more other QoS requirements.In an example, a WTRU may be configured by an upper layer to transmit apacket with the highest priority, e.g., regardless of other timing, rateor efficiency-related QoS requirements.

The example communication system described herein may allow and/orenable other WTRU behaviors including, for example, random access forTRP, changing and/or monitoring of a control channel, grant and/ortransmission parameter selection, SR method selection, and/or the like.

As described herein, a WTRU may be configured to determine that one ormore QoS requirements related to a transmission (e.g., an uplinktransmission) may not be met. Such QoS requirements may be timing and/orrate related (e.g., such as those described herein), for example. Theinability to meet the QoS requirements may, for example, lead to achange of an applicable procedure, a change of a transmission scheme,and/or a change to other transmission-related behaviors. For example,the WTRU may attempt an uplink transmission using a first transmissionscheme. The WTRU may determine whether or not a QoS requirement such asa timing-related or a transmission rate-related requirement describedherein can be met using the first transmission scheme (e.g., for atleast a subset of the data available for transmission). If the WTRUdetermines that the QoS requirement may not be met using the firsttransmission scheme, the WTRU may adjust its operations in order to meetthe QoS requirement. For example, the WTRU may autonomously adjust thetransmission scheme used for the transmission. The adjustments, whichmay include an increase to, a change to, or a reduction of the resourcesused for transmission, may result in changes in one or more operationalaspects of the transmission scheme (e.g., one or more transmissionparameter changes).

When changing transmission schemes, the WTRU's connectivity to thenetwork may be affected/changed. Thus, connectivity type may be anexample of an operational aspect that may vary between differenttransmission schemes. For example, upon changing the connectively type,the WTRU may initiate an access procedure and/or request areconfiguration procedure with the network (e.g., an L3reconfiguration). In an example, the WTRU may initiate an RRC procedurethat requests a reconfiguration of its connectivity. The request mayinclude one or more of the following. The request may include anidentity of an applicable logical data grouping (e.g., LCH, LCG, SOM,and/or the like). The request may include information related to theQoS-aspect that triggered the request for change in connectivity (e.g.,the amount of resource adjustment, rate or timing for an improvement,etc.). The request may include information related to the data to betransmitted (e.g., head-of-queue delay or average delay, the amount ofoutstanding data, etc.). The WTRU may include a measurement in therequest.

The WTRU may initiate a TRP access and/or a random access. For example,the WTRU may initiate an access to the system for purposes of increasingthe amount of resources available, changing the type of resources,modifying the amount of associated TRPs, and/or the like. The WTRU maydetermine (e.g., from measurements of a reference signal such as asignature) that one or more TRPs may be in the WTRU's range. The WTRUmay determine suitable random access resources (e.g., using informationincluded in in an access table). The WTRU may initiate the transmissionof a preamble on such resources. The foregoing operations may lead to adifferent set of resources available to the WTRU (e.g., the resourcesmay increase or decrease, and/or there may be a different set of controlchannels to monitor). For example, the WTRU may initiate an increase ofthe set of available resources, which may lead to an aggregation of morephysical layer resources, more carriers, additional TRPs and/or Uuinterfaces with network entities (e.g., the network entities may includeeNBs and/or TRPs, the interface may be via dual connectivity or asimilar technology, etc.).

When changing transmission schemes, the WTRU may expand or modify theidentity and/or number of control channel that the WTRU is monitoring.Thus, the set of one more control channels monitored by the WTRU may bean example of an operational aspect that may be varied for differenttransmission modes. For example, the WTRU may determine that differentand/or additional control channels are available for schedulingtransmissions. The WTRU may request and/or activate these controlchannels. The WTRU may perform the determination following thetransmission of a signal (e.g., to a network). The signal may indicate arequest to activate such control channels. In an example, the WTRU mayperform the determination in a manner similar to performing an access tothe system (but for the same signature and/or cell). The WTRU may switchand/or add control channels. For example, the WTRU may switch to and/oradd a control channel that is associated with a different SOM (e.g., thecontrol channel may be associated with different physical layerresources, different physical data channels, and/or a differentnumerology).

When changing transmission schemes, the WTRU may expand and/or modifyavailable resources. Thus, the set of available resources may be anexample of an operational aspect that may be varied for differenttransmission modes. The WTRU may determine that a different set ofresources is available. The WTRU may switch to a different set of DCIsand/or DCI types. For example, the WTRU may determine that it mayattempt to decode a different set of DCIs on a control channel. SuchDCIs may be associated with a different SOM, a different numerology, adifferent set of PRBs, and/or the like. The WTRU may update its controlchannel monitoring activities (e.g., DRX may be updated). For example,the WTRU may change its monitoring frequency or intensity for a controlchannel (e.g., to start decoding more intensely). The WTRU may enter anactive mode for a control channel when more resources are desired. TheWTRU may select a scheme for scheduling requests based on QoSrequirements (e.g., as a function of the QoS requirements). For example,the WTRU may select a specific scheme for obtaining transmissionresources based on the QoS requirements associated with the data to betransmitted (e.g., as a function of the QoS requirements). The WTRU mayuse a contention-based transmission scheme if the WTRU determines thatapplicable QoS requirements for the data can be met. The WTRU may use adedicated SR resource for transmission if the WTRU determines that anapplicable QoS requirement for the data may not be met. If the WTRUdetermines that a plurality of resources and/or request schedulingschemes are available, the WTRU may select a request scheduling schemeand/or resources associated with a SOM if the scheme and/or resourcesmay enable a transmission that meets the applicable transmissionrequirements.

When changing transmission schemes, the WTRU may modify and/or select aspecific transmission parameter or a grant. Thus, transmissionparameters and/or grants may be an example of an operational aspect thatmay be varied for different transmission modes. For example, the WTRUmay determine that a different set of transmission parameters areavailable and/or may be used for data transmission. The WTRU may selecta grant among a plurality of grants such that one or morecharacteristics of the data transmission may be modified. Suchcharacteristics may include reliability, HARQ operating point, diversityapplied to the transmission, transmission power, etc.

When changing transmission schemes, the WTRU may modify multiplexing,assembly, and/or segmentation techniques and/or rules associated withthe data transmission. Thus, multiplexing, assembly, and segmentationmay be examples of an operational aspect that may be varied fordifferent transmission modes. For example, a WTRU may change itsmultiplexing rules, assembly and/or segmentation rules, and/or the like,when creating MAC PDUs for transmission of data. For example, the WTRUmay skip segmenting packets at the MAC layer when dealing with data forwhich a QoS requirement may not be met.

A WTRU may be configured to maintain and/or react on latency-relatedcharacteristics or criteria (e.g., a time-related QoS requirement) for afirst subset of data, but not for a second subset of data. The firstsubset of data may be associated with a first logical channel, a firstflow, a first service, a first data type, and/or the like. The secondsubset of data may be associated with a second logical channel, a secondflow, a second service, a second data type, and/or the like. In anexample, rate-related criteria may be associated with a specific set ofone or more logical channels, but not for other logical channels. In anexample, QoS requirements may be provided with packets from upper layerson any logical channel or flow. The QoS requirements may be provided onan as-needed basis.

When changing transmission schemes, the WTRU may provide the networkwith information associated with the uplink data that the WTRU isattempting to transmit. For example, a WTRU may transmit QoS-relatedinformation. The WTRU may transmit the QoS-related information alongwith relevant data packets, SDUs, and/or collection of bytes (e.g., in aMAC PDU). For instance, the WTRU may transmit a TTL with its associatedpackets, SDUs, and/or collection of bytes. The TTL (or an absolute time)may be represented in time units (e.g., milliseconds). The TTL mayoccupy the least significant portion of an absolute time (e.g., to allowthe recipient to determine what the absolute time may be).

QoS-related information may be appended to relevant data. A receivingentity of the data with which the QoS-related information is sent may bea network node (e.g., a base station), or a receiving WTRU. Thereceiving entity may be involved, for example, in data operations suchas relaying and/or forwarding, e.g., such as an eNB configured to enableV2V communications (e.g., by forwarding UL transmissions directly to adestination). The receiving entity may use the QoS-related informationto determine how to process the received data. The receiving entity(e.g., a base station) may determine and/or modify a best or preferredpath, a resource, a TTI, a SOM, and/or the like associated withtransmitting the data to a final destination. The receiving entity maymodify and/or prioritize its processing of the received data accordingto QoS requirements. For example, the receiving entity may modify and/orprioritize the enforcement of resource reception priority (e.g., in thecase of RF or base-band limitations). The receiving entity may modifyresources, RATs, and/or mechanisms (e.g., SC-PTM versus unicast versuseMBMS) that are used to relay the received data. The receiving entitymay select a path for relevant cell(s) or network(s) to forward thedata. For example, the receiving entity may determine whether to sendthe data to an application server in the network or send the data to aproxy application service located in a cell or TRP.

Time-related requirements (e.g., such as those related to latency) mayhave various representations in a WTRU. The WTRU may use the time-basedrequirements as criteria for determining when the WTRU should switchfrom a first transmission scheme to a second transmission scheme. Forexample, the WTRU may maintain latency requirements. The WTRU mayobtain, e.g., from an upper layer, transmission latency requirements.The WTRU may use such requirements to, for example, make schedulingdecisions and/or resource usage decisions, to guide aspects related tothe request of resources, to perform multiplexing/de-multiplexing,and/or to control transmissions. For instance, the WTRU may maintainand/or monitor a TTL parameter that may be representative of the timeelapsed from the reception of a data packet until a successfultransmission of the data packet. The WTRU may utilize the TTL parameterat a transmission stage (e.g., at each transmission stage) to adjust abehavior, a procedure, and/or the like in a way to meet a time-relatedQoS requirement. The WTRU may maintain the TTL for a packet, a SDU, acollection of bytes, and/or the like. The TTL may be associated with anamount of time allocated to successfully complete a transmission overthe air interface.

The WTRU may perform a specific operation (e.g., within its transmissionstack) to change the WTRU's behavior when the TTL reaches a certainvalue or exceeds a certain range. For example, the WTRU MAC may decideto initiate an autonomous transmission using one or more of thetechniques described herein (e.g., use contention-based resources) whenthe TTL associated with a MAC PDU has reached a certain threshold.

The MAC may decide to utilize one HARQ type over another, one TTI overanother, one transport channel over another, and/or one coding rate overanother when, for example, the TTL associated with a MAC PDU has reacheda certain threshold. Thus, a TTI length, a transport channel identity, acoding rate, etc. may be examples of an operational aspect that may bevaried when the WTRU changes transmission schemes. The WTRU may decideto trigger a specific request for resources (e.g., on a certain SOM)from the network, or to use a different mechanism to issue such arequest, when the TTL has reached a certain threshold.

It should be noted that the notion of TTL as used here is not limited toany one particular definition. For example, the notion of TTL mayencompass any mechanism for defining and representing one or more QoSrequirements. Thus, some examples may be described with respect to usinga TTL to determine when to switch transmission schemes and/or change atransmission parameter, but other information indicative of one or moreQoS requirements may also be used as a criteria for determining when toswitch transmission schemes and/or change a transmission parameter.

The example communication system described herein may be characterizedby features related at least to requests, determination, and access ofsuitable transmission resources. For example, these features may berelated to the scheduling and/or determination of one or more applicablecontrol channels (e.g., SOM-specific control channel).

The example communication system described herein may be characterizedby a unique mechanism for requesting network access (e.g., access tosuitable resources) in order to meet a specific QoS requirement (e.g., atime-related QoS requirement). In one example embodiment, a WTRU maysend a resource request (RR) to the network. The RR may include arequest for new or modified resources and/or may indicate a bufferstatus. The RR may include a request for a change of connectivity to thenetwork. The RR may include request for a change of resources. The RRmay include a request for a change of the control channels to bemonitored or configured. The RR may include a request for a change ofTRPs. The RR may include a request for a change of SOMs. The RR mayinclude a request for a change of another aspect as described herein.

An RR may indicate QoS related parameters and/or may provide anindication or potential indication of a failure to meet QoSrequirements. In order to meet QoS related requirements, differentresource request mechanisms and/or formats may be defined and used fordifferent services, logical channels, logical channel groups, and/or QoSgroups. The type of an RR may be determined based on one or more QoSparameters reaching a certain threshold. An RR may be sent based on theone or more QoS parameters reaching a certain threshold (e.g., TTLreaching a threshold).

An RR may be characterized by the type of transport format used, thetype of resources in which the RR is transmitted, information providedwithin the RR, TTI length used for RR transmission, SOMs, and/or thelike. A WTRU may determine which RR to use based on one or more QoScharacteristics.

Information transmitted in an RR may include, for example, a request forresources, a request for modification of assigned resources, anindication of buffer status, and/or an indication of a failure or apotential failure to meet certain QoS requirements. An RR may include anindication of an intention to transmit in an upcoming resource and/orthe resource the RR plans on using. An RR may include an indication thatresources are being requested in order to meet certain QoS requirementsassociated with the data for which the RR was triggered. In someexamples, such an indication may be the only information provided in anRR. In other examples, additional information such as information abouta transmission and/or a transmitting WTRU may be provided in an RR.

The WTRU may, in an RR, identify one or more of the specific services,SOMs, and/or LCGs to which the RR applies. In an example, the indicationcomprised in the RR may signal a request to allocate additionalresources for the SOM/transport channel in which the RR is beingtransmitted (e.g., assuming distinct physical resources are used fordifferent SOMs/transport channels). The WTRU may transmit multiple RRs(e.g., one for resources associated with each SOM) in a single SOM. AnRR (e.g., each of the multiple RRs) may signal a request for resourcesassociated with a different SOM. The association between an RR and theSOM for which the RR is being sent may be based on a tag (e.g., the tagmay be included in the RR), based on the resources used (e.g., locationof bits in time or frequency or both), based on other physicalcharacteristics of the RR transmission (e.g., transmit power/energy,modulation schemes, etc.), based on the format of the RR, based on thesize of the RR, based on the timing (e.g., when the RR is sent by theWTRU) of the RR, and/or the like.

An RR may indicate a request for additional transmission resourcesand/or whether currently allocated resources are sufficient (e.g., withrespect to data of a specific service or a logical channel, or withrespect to a specific SOM). An RR may request additional resourcesdynamically (e.g., relative to a previous transmission). For example, aWTRU may transmit an RR in order to gain access to an additionalresource that may be allocated shortly after or immediately following aprevious transmission. An RR may request resources relative to an amountof currently allocated resources in the WTRU. For example, the WTRU mayrequest and/or be configured with a specific amount of resources perunit of time (e.g., the resources may be guaranteed or reserved) for theWTRU's use for a finite period. Following configuration of suchresources, the WTRU may send an RR (e.g., a new request) or anindication to reduce or increase the amount of resources alreadyprovided to the WTRU.

An indication in an RR may have a certain value. For example, theindication may take one of two possible values (e.g., a 1-bit value).The indication may take a first value if, for at least one PDU, theexpected time of successful completion of transmission exceeds thecurrent time plus the TTL of the PDU. The indication may take a secondvalue otherwise. In another example, an indication in an RR may take oneof four possible values (e.g., a 2-bit value). A WTRU may determine, foreach PDU, the difference between the expected time of successfulcompletion and the sum of the current time and the TTL of the PDU. TheWTRU may set the value of the indication based on the highest suchdifference across all PDUs to be transmitted. The indication may be setto a first value if the difference exceeds a first threshold, to asecond value if the difference exceeds a second threshold (but does notexceed the first threshold), to a third value if the difference exceedsa third threshold (but does not exceed the second threshold), and to afourth value otherwise. The values of the thresholds may be pre-definedor signaled by a higher layer. Increasing the number of possible valuesfor the indication may allow for a faster or more accurate adjustment ofthe allocated resources.

In certain options or for certain RR types, an RR may includeinformation derived from QoS-related scheduling information as describedherein. For example, a WTRU may transmit latency-related or anyQoS-related information to a receiving node. The information may betransmitted in the RR, in a MAC PDU, or in an RRC signaling message. Theinformation may be used by the network, for example, to scheduleresources and/or prioritize among different WTRUs that requireresources. The information that may be included (e.g., by a WTRU) in anRR may take on or be a function of one or more of the following forms.

A WTRU may include, in an RR, information associated with a TTL. Forexample, the WTRU may include a minimum TTL, or a TTL for a packet, aPDU, etc., that is currently queued at the WTRU for transmission. TheWTRU may maintain multiple transmission queues that may be latencycritical. The WTRU may transmit a TTL for each head-of-queue of themultiple transmission queues.

A WTRU may include, in an RR, information associated with a buffer size.For example, the WTRU may include the buffer size of data that areconfigured with a TTL requirement, the buffer size of data that can bemultiplexed for the service(s) that triggered the request, or the buffersize of all of the data in the WTRU (e.g., together with theirassociated priority and/or requirements).

A WTRU may include, in an RR, information associated with a timing rangefor a specific packet, a PDU, etc., and/or their respective buffersizes. For example, the WTRU may transmit minimum and maximum values foran acceptable latency range for a PDU or a set of data.

A WTRU may include, in an RR, information associated with an absolutetime for transmitting/receiving a packet or an amount of data over theair, or a range of absolute times for acceptable latency. A WTRU mayinclude, in an RR, information associated with a QoS class or anabsolute priority of data, rate related information, and/or the expectedtime for successfully completing the transmission of at least one PDU(e.g., given currently allocated resources). The expected time may inturn be a function of one or more of the following. The expected timemay be a function of an expected time at which the PDU can be includedin a transport block submitted to the physical layer for a first timeunder a set of given prioritization rules. The expected time may be afunction of an expected time for a retransmission. One of more of theparameters described herein may be set to a pre-defined value or besignaled by a higher layer.

A WTRU may include, in an RR, information associated with a specific TTIthat the WTRU may use on resources (e.g., 2 symbol or 0.5 ms), thenumber of resource blocks per time unit (e.g., the number of resourceblocks in a fixed period of x frames), and/or the frequency range inwhich such resources may be located (e.g., in a specific narrowbandwidth supported by the WTRU, or preferred by the WTRU due to radiocharacteristics of the WTRU).

A WTRU may indicate (e.g., implicitly indicate) specific RR-relatedinformation through the selection of resources, timing, encoding, power,and/or the like that are associated with transmission on PHY resources.For example, a WTRU may indicate the amount of additional resources tobe allocated to the WTRU based on the time/frequency resource it uses tosend the RR. RR-related information may be indicated by the formatand/or transport mechanism used in RR transmission. The RR may betransmitted, for example, in the PHY layer (e.g., on a specific PHYcontrol channel or piggybacked with data) and/or in the MAC layer (e.g.,using a MAC CE and/or the like). The RR may be transmitted entirely inthe PHY layer. When transmitted in the PHY layer, the RR may betransmitted via one or more of the following.

An RR may be transmitted using a single OFDM symbol or using a singlesymbol in one of the resource blocks associated with the WTRU's uplinktransmission (e.g., at a pre-defined or configured location). In anexample, the RR may be transmitted in the last symbol(s) (e.g., lastsymbol(s) in time) of the OFDM subcarrier that has the largest index orindices. The RR may be transmitted using an uplink control channel or aspart of the WTRU autonomous scheduling information that may betransmitted in an uplink control channel.

An RR may be transmitted using dedicated PHY resources, the location ofwhich may be provided to the WTRU via signaling in the network (e.g.,RRC signaling) or obtained through information included in an accesstable sent to the WTRU. The RR may be transmitted (e.g., in conjunctionwith the foregoing) using identity or timing related information (e.g.,to derive the location of PHY resources).

An RR may be transmitted using contention-based resources such a RACH orsimilar signaling. The contention-based resources may be spread over PHYresources being utilized by other WTRUs in such a way as to minimize theoverall interference with those WTRUs (e.g., using CDMA or puncturingsuch that a few/small number of interfered resource elements associatedwith a specific WTRU are used). In an example case of LTE-assisted5Gflex tight interworking, a WTRU may be configured to transmit an RRover the LTE PUCCH. The PUCCH SR may be extended to carry informationthat the request is related to with QoS characteristics that can be metby a 5G system. More specifically, the SR may indicate that the WTRU isrequesting 5G resources. This may be enabled, for example, by changingthe SR format to include an additional bit, by reserving specialresources in which a SR-triggered 5G request is sent, and/or the like.

A WTRU may have access to multiple sets of resources or mechanisms fortransmitting an RR. For example, for different services, the RRs may bedefined with different characteristics including, for example, differentformats or types, different values of time to transmit (e.g., time fromtriggering the request to transmitting the request over the air),different symbols, different signaling mechanisms, different transportformats, and/or the like. The WTRU may be able to select from thesedifferent mechanisms based on one or more of the following. The WTRU mayselect a mechanism for transmitting an RR based on the latencycharacteristics of the data in a queue or the data to be sent (e.g., thedata may or may not be latency critical). The WTRU may select amechanism for transmitting an RR based on the TTL of one or more packetsor data to be sent (e.g., the TTL may or may not be relative to athreshold). The WTRU may select a mechanism for transmitting an RR basedon the priority of data or service type. The WTRU may select a mechanismfor transmitting an RR based on one or more of the QoS requirementsdescribed herein (e.g., time-based or rate-based QoS requirements). Forexample, the WTRU may send an RR for a service (e.g., ULLRC or eMBB) thePHY using different TTIs, for example, depending on the timecriticality, priority, and/or timing requirements of the data in abuffer(s) for which the RR is sent/triggered.

An RR for a SOM (e.g., for each SOM) a given service or a logicalchannel may have different characteristics related to how the RR istransmitted in the PHY layer. In an example, the RR may be transmittedwith different coding schemes, over different transport channels, usingdifferent TTIs and diversity/reliability, using dedicated (e.g., versusshared/contention-based) resources, and/or using othermechanisms/techniques. A WTRU may utilize different RR mechanismsdepending on the SOM or service involved. For instance, a WTRUconfigured with a ULL service may employ a 1-bit PHY layer RR mechanismto request resources for the ULL service, while the WTRU may employ aMAC layer RR if a buffer status in conjunction with RR at the PHY layerindicates a request for IBB-type services.

A WTRU may trigger an RR based on one or more of the following. The WTRUmay trigger an RR based on a QoS requirement (e.g., a QoS-related event)described herein. For example, the WTRU may trigger an RR based on alatency-related event. Such a latency-related event may comprise thearrival of a time critical packet at the MAC layer or a higher layer,for example. The WTRU may trigger an RR based on the TTL of one or morepackets or data falling below a threshold. The WTRU may trigger an RRbased on the initiation, configuration or reconfiguration of a service,a TRP, a logical channel, a SOM, and/or the like at the WTRU. The WTRUmay trigger an RR based on the arrival of a packet with a different QoSclass than an ongoing transmission. The WTRU may trigger an RR based ondata not meeting rate-related QoS requirements, and/or the like.

A WTRU may trigger an RR based on one or more of the following. The WTRUmay trigger an RR based on an indication from the application layer. TheWTRU may trigger an RR based on periodic expirations of a timer. TheWTRU may trigger an RR based on an indication that a buffer is no longerempty (or other buffer occupancy information). The WTRU may trigger anRR based on one or more HARQ entities indicating that retransmission isto be performed upon returning from sleep, DRX and/or the like. The WTRUmay trigger an RR based on the initiation, configuration orreconfiguration of a service. The WTRU may trigger an RR based on thecreation of a logical channel (e.g., a logical channel requiring lowlatency communication). The WTRU may trigger an RR based on the WTRUbeing connected to the network. With respect to the last example triggerevent, if the network is an LTE assisted network and if new data arriveswith requirements that cannot be met by LTE services, the WTRU maytrigger a 5GFlex RR.

A WTRU may trigger an RR for a service or a logical channel while atransmission of data on a resource that is serving another service oranother logical channel is ongoing or has started. In this scenario, theWTRU may perform one or more of the following actions, for example,based on a determination of priority, an amount of resources, and/or anamount of data to send (e.g., in absolute terms or based on current QoScharacteristics for each service). The WTRU may append RR information tothe ongoing data transmission or the WTRU may delay the transmission ofthe RR until the ongoing data transmission is completed. For timesensitive transmissions, however, RR delay may not be performed if theWTRU delays the transmission of the RR, or if the appended informationis decoded by the network at the end of a TTI. The WTRU may immediatelysend the RR to the network. The WTRU may avoid transmitting the RR, andperform resource prioritization to address the new service thattriggered the RR using existing resources.

To illustrate, a WTRU may have an ongoing web-browsing session and mayhave resources available for a transmission. If at that time the WTRUreceives data with less stringent QoS requirements (e.g., time-relatedQoS requirements), the WTRU may transmit resource request informationtogether with the data (e.g., using a MAC PDU or embedding the RR in thePHY layer). If the data received has strict QoS requirements or if alatency requirement is not being met, the WTRU may trigger thetransmission of an RR using the RR characteristics associated with theservice (e.g., the RR characteristic used for transmission of the RR mayimplicitly indicate the service to which the RR applies; the RRcharacteristics may be reflective of numerology, timing, resources,transmission techniques, and/or the like). In such a case, the WTRU maytransmit the RR in parallel with the ongoing data transmission (e.g., ondifferent resources), or the WTRU may delay the transmission of data totransmit the RR. For example, if the data arrives in the middle of anongoing transmission and an RR is triggered, the WTRU may transmit(e.g., immediately transmit) the data in the first available resource.If the next available resource occurs at a later time than the time fortransmitting the corresponding RR on the air interface, the WTRU maytransmit the RR during an ongoing transmission. Mechanisms fortransmitting an RR while the transmission of a longer TTI is ongoingand/or while RR specific resources are limited or unavailable aredescribed herein.

In the example communication system described herein, a WTRU may obtainaccess to resources through a grant from the network. Whether to usegranted resources may be an example of an operational aspect that may bevaried when switching transmission schemes. The WTRU may receive one ormore of the following in the grant. The WTRU may receive information(e.g., an indication) about resources that the WTRU may access. Theresources may be specified as a pre-configured resource index or beexplicitly signaled in the grant, for example. The WTRU may receiveinformation about a SOM or transport channel for which the grant isvalid. For example, the information may indicate a numerology, a TTI,and/or a waveform that the WTRU may use. The WTRU may receiveinformation about a logical channel, service type, priority, and/or thelike that the WTRU may use for the given grant. The information mayinclude an identifier or value that is commonly understood between theWTRU and the network. The WTRU may receive information about thetransport format of the grant (e.g., such as MCS, block size, startingtime, etc.). The WTRU may receive information about a TTI length. TheWTRU may receive information about the validity of the grant. Forexample, the information may indicate a TTI or range of TTIs that theWTRU is allowed to use for the grant, period lengths, etc. The WTRU mayreceive information about a range of logical channel, priority, and/orservice that is usable with the grant or that may be excluded from thegrant. The range may be greater or less than a certain priority value(e.g., which may be indicated by the network in the grant).

A WTRU may prioritize the transmission of logical channels. Suchprioritization of logical channel transmission may be an example of anoperational aspect that may be varied when the WTRU switchestransmission schemes. For example, the WTRU may utilize a grant totransmit a logical channel (e.g., any logical channel) that has apriority value less or greater than a value signaled in the grant, or iswithin a certain range (e.g., from a min value to a max value) signaledin the grant. Within the range of allowable priority values, the WTRUmay exclude certain priority levels.

A WTRU may be configured to prioritize the use of granted resources. Theprioritization of granted resources among various services may be anexample of an operational aspect that may be varied when the WTRUswitches transmission schemes. For example, the priority range of 5Gservices may include ten different priority levels associated with thescheduling and usage of granted resources, with level ten being thehighest priority that may be associated with an ULLC service type. AWTRU may be configured to designate resources first for higher priorityservices (e.g., when those higher priority services have data totransmit). For example, a WTRU may receive a grant that is assigned apriority level of five. As such, the WTRU may be configured to utilizethe grant (e.g., resources associated with the grant) for a transportblock tagged with a priority level of five or higher, or for a transportblock with the highest priority if the highest priority is less thanfive. The MAC layer, upon receiving an indication of the grant from thePHY layer, may select a packet in its transmission buffer with apriority level of five or higher, or with the highest priority if thehighest priority is less than five, and may send that packet to the PHYlayer for transmission.

A WTRU may be configured to tie resource prioritization to a specifictype of resources at the PHY layer. Tying resource prioritization toresource types may be an example of an operational aspect that may bevaried when the WTRU switches transmission schemes. For example, theWTRU may be configured to use a specific SOM only for a logical channelof a specific priority. To illustrate, a WTRU may receive a grant thathas been assigned a priority level of five. The WTRU may be configuredto utilize the grant (e.g., resources associated with the grant) for atransport block tagged with a priority level of five or lower. As such,the WTRU may be prevented from utilizing the resources associated withthe grant for higher priority data (e.g., data with a priority levelhigher than five) since those resources may not be configured (e.g.,with respect to reliability or timeliness) to accommodate data of higherpriority levels.

A WTRU may be configured to exclude specific priority levels from therange of priority levels for which a granted resource may be used. Theexclusion of specific priority levels may be an example of anoperational aspect that may be varied when the WTRU switchestransmission schemes. The specific levels that may be excluded by theWTRU may be defined through a specification or may be signaled to theWTRU. For instance, a priority level of ten may be excluded since thelevel may be associated (e.g., may be always associated) with thehighest form of ultra-low latency communication, and as such may requirea special type of resources that may be granted separately (e.g., byindicating the special priority level, or via a different mechanism).

A WTRU may be configured to autonomously access resources (e.g.,preconfigured resources). Autonomous access of resources may be anexample of an operational aspect that may be varied when the WTRUswitches transmission schemes. A WTRU may be pre-configured with a setof transmissions that the WTRU may autonomously perform. Such acapability may be desirable, for example, in IoT applications,industrial applications, vehicular communications, and/or the like. Inone or more of those scenarios, a WTRU may move from having few or nouplink transmissions for a long period of time to having regular (e.g.,periodic) transmissions with very low latency. To start regulartransmissions with low latency, the WTRU may be configured with a set ofpre-configured resources. The WTRU may use one or more of thesepre-configured resources to transmit data with certain QoS requirements.For example, the WTRU may be configured with resources for UL, DL,Sidelink, etc. Such configurations may not necessarily reserve resourcesfor the WTRU, but may indicate to the WTRU which resources the WTRU mayutilize when needed.

A preconfigured resource may include a static configuration of one ormore overlapping or non-overlapping time-frequency resources. Theresources may last a finite period of time and/or may occur with acertain periodicity. For example, one pre-configured resource mayinclude a single resource block located at a specific frame or subframenumber. A WTRU may receive pre-configured resources or requestmodification of pre-configured resources upon registration and/orconnection to the network, via dedicated signaling from the network(e.g., similar to RRC signaling), via an access table (e.g., inassociation with the system signature), through the use of an identitycorresponding to the WTRU or a service, and/or by establishing aservice, a radio bearer, a logical channel and/or the like that mayrequire such pre-configured resources.

A WTRU may gain access to a pre-configured resource through a shortuplink transmission or via a transmission of an RR or schedulinginformation (SI), for example. Such an uplink transmission may includeone or more of the following. The transmission may include a request totransmit. The transmission may include an index or an identifier thatidentifies the desired pre-configured resource in a pre-configuredresource set. The transmission may include information that specifiesthe duration of use of the pre-configured resource (e.g., such aswhether the WTRU wishes to use the resource once or periodically, thetime duration for which the WTRU wants to use the resource, etc.). Thetransmission may include conditions that may potentially be used todefine whether and/or when the pre-configured resource is no longervalid The transmission may include a request for an identifier/index andother timing-duration related information about the pre-configuredresource The transmission may include time periods in which the WTRU mayuse a preconfigured resource. The transmission may include otherinformation that may be carried in an RR or SI. The WTRU may beidentified in the transmission, for example, by a WTRU specific RR or aSI resource, or by an explicit identifier as described herein.

Upon transmitting a request (e.g., an RR as described herein), a WTRUmay start monitoring one or more control channels associated with theservice or QoS class that triggered the request. For example, iftransmission of low latency data is requested, the WTRU may initiatemonitoring of one or more control channels associated with the lowlatency service, or the corresponding SOM. The WTRU may receive aconfirmation in a timely manner (e.g., in ways similar to what isdescribed herein). The WTRU may receive a response from the networkafter sending a short uplink transmission, as described herein. The WTRUmay receive, from the response, either or both of the following: anindex and/or timing related information that may be in the short uplinktransmission, or an acknowledgement for the use of a resource. Forexample, the WTRU may perform a short UL transmission indicating arequest for resources for a specific service or SOM. The network mayrespond with the index for the pre-configured resource. Depending on thepre-configuration conditions and/or the type of service requested, thepre-configured resource may be used for at least one transmission.

A WTRU may be provided with pre-configured resources in the downlink(DL). For example, a provision may be made using a response mechanism asdescribed herein (e.g., the provision may be included in a response fromthe network). The WTRU may disable pre-configured resources (e.g.,similarly to how pre-configured resources may be enabled). For instance,the WTRU may disable (e.g., implicitly) a pre-configured resourcetransmission through the transmission of an RR, e.g., when the amount oflatency critical data in the buffer is below a threshold. Request forand/or enablement/disablement of pre-configured resources are examplesof an operational aspect that may be varied when the WTRU switchestransmission schemes.

A WTRU may perform an autonomous uplink transmission, for example usingpotential resources that may not necessarily be allocated to the WTRU.For such transmissions, the WTRU may enable the utilization ofpreconfigured resources and/or to inform the network that such resourcesare being utilized by the WTRU. Additionally or alternatively, the WTRUmay perform the uplink transmission on a low-latency uplink controlchannel or via a low-latency data transmission (e.g., with a short TTI)that is assigned to the WTRU or dedicated for one or more WTRUs.Autonomous uplink transmission is an example of an operational aspectthat may be varied when the WTRU switches transmission schemes.

A WTRU may perform an UL transmission for enabling a preconfiguredresource via a MAC CE or other similar control messages over resourcesscheduled for uplink transmissions. The WTRU may perform the foregoinginstead of sending the UL transmission autonomously. Using scheduledresources to enable preconfigured resources may be an example of anoperational aspect that may be varied when the WTRU switchestransmission schemes.

The WTRU may transmit a request for pre-configured resources, or anindication to use preconfigured resources via any suitable techniquedescribed herein. For example, the WTRU may transmit the request orindication in a manner similar to transmitting an RR. For example, theWTRU may enable a preconfigured resource via an RR (e.g., based on thecontent of the RR). The WTRU may enable a preconfigured resourceexplicitly, for example, by sending an RR to indicate a desired resourceconfiguration. The WTRU may enable a preconfigured resource implicitly,for example by including a QoS related parameter in an RR that may beinterpreted as an automatic request for a specific type of resourceconfiguration. The WTRU may implicitly enable the use of apre-configured resource upon transmission of an RR comprising specifictriggering conditions. Such conditions may be part of an initialpre-configuration of the pre-configured resource itself. For instance,the WTRU may be configured to utilize the pre-configured resource upontransmission of an RR that indicates an amount of latency critical datathat is above a specific threshold.

A WTRU may be configured to perform the uplink transmission describedherein using one or more of the following mechanisms. The WTRU may beconfigured to perform the uplink transmission using a short PHY layersignal reserved for one or more WTRUs to signal the network. The WTRUmay be configured to perform an uplink transmission using a CDMA-likesignal or a punctured signal sent over a channel shared among multipleWTRUs. The WTRU may be configured to perform an uplink transmissionusing a RACH-like uplink transmission performed at specific,well-defined time instances. The WTRU may be configured to perform anuplink transmission via an initial transmission on one of the resourcesassociated with a pre-configured resource. Network transmissions in thedownlink (e.g., which may include an ACK or an indication) may beperformed using a low-latency control channel, a data channel with ashort TTI, or another suitable DL channel.

A WTRU may be allocated resources to transmit data for one or moreservices. The WTRU may dynamically schedule (e.g., via self-scheduling)data transmission using all or a subset of the allocated resources. Theallocated resource may be constrained within one or more specificwindows in the time domain (e.g., such time windows may have a durationof a few to several milliseconds). In certain embodiments, the one ormore time windows may recur periodically (e.g., substantiallyperiodically). The allocated resources may be constrained within acertain range in the frequency domain. The range of frequencies may be afunction of time (e.g., to provide frequency diversity). The allocatedresources may be used by at least one uplink physical channel (UPCH) onwhich the WTRU may transmit data and control information. The allocatedresources may be used by one or more sidelink physical channels (SPCHs).Resources may be allocated based on service type (e.g., for each type ofservices) such that some resources may be reserved for certain types ofservices.

A WTRU may be allocated resources to transmit scheduling information(SI), other uplink control information (UCI), and/or sidelink controlinformation (SCI). These information may include, for example, HARQ-ACKand/or CSI feedback. It should be noted that the discussion herein withrespect to SI may be applicable to a resource request (RR) (e.g., an RRmay be regarded as a type of SI and be referred to interchangeably withSI; e.g., examples described in terms of SI may also be applicable to RRand vice versa). Similarly, the discussion herein with respect to an RRmay be applicable to SI. For example, while the foregoing discussesresource allocation for transmitting SI, a person skilled in the artwill understand that the mechanism may be applicable to the transmissionof an RR. The resources allocated for the transmission of SI and/orother UCI/SCI may be part of the block of resources allocated forself-scheduling operations, or may be allocated separately. In certainembodiments, the resources may be made available to transmit data. Thetransmission of SI and/or other UCI/SCI may take place on a specificphysical control channel (e.g., an uplink or sidelink physical controlchannel). The SI and/or other UCI/SCI may be encoded and multiplexed(e.g., in-band) in an uplink or sidelink physical channel (e.g., alongwith data).

Resource allocation for the transmission of SI and/or other UCI/SCI maybe configured to occur at regular intervals, such as at every shortestapplicable TTI, so as to provide frequent opportunities fortransmission. Resources used for the transmission of a single instanceof SI may occupy a full range in the frequency domain of the allocation.This way, the number of time symbols configured for transmitting oneinstance of SI may be reduced (e.g., minimized). The SI may be jointlyencoded with other UCI/SCI. The SI and/or other UCI/SCI may beseparately encoded and multiplexed (e.g., concatenated) prior tomodulation, layer mapping and/or resource element mapping. The codingrate, coding scheme and/or modulation may be determined using one ormore of the techniques described herein.

A WTRU may transmit information about the parameters associated with thetransmission of SI and/or UCI/SCI. Such information may help a receivingnode, such as a network node or another WTRU, decode the SI and/orUCI/SCI. For example, a WTRU may specify the number of information bits,the modulation and coding scheme, and/or resource information (e.g., thenumber of time symbols) associated with the SI and/or UCI/SCI. Suchinformation may be encoded separately from the SI and/or UCI/SCI, and/ormay be mapped to a known portion of an allocated resource. The WTRU mayinclude an indication (e.g., for each time symbol that includes SIand/or UCI/SCI) of whether the next time symbol includes SI and/orUCI/SCI.

A WTRU may transmit data in one or more TTIs. The WTRU may transmit datafor one or more services, one or more logical or transport channels,and/or one or more receivers (e.g., network nodes or other WTRUs). TheWTRU may include information associated with the data in SI (e.g., aninstance of SI) to help the one or more receivers decode the data. Theinstance of SI may be transmitted prior to the data transmission in theone or more TTIs. The transmission of SI may be in accordance with afixed timing relationship.

A WTRU may indicate in SI whether or not a transmission of data istaking place in a TTI. For example, the SI may indicate one or more ofthe following about a TTI or an applicable type of transmission withinthe TTI. The SI may indicate whether data is transmitted in the TTI. TheSI may indicate the type of data, service or logical channel included inthe transmission. The SI may include a timing indication for the TTI(e.g., how many time units from the SI instance). The SI may indicatethe duration of the TTI. The SI may indicate an identifier for the WTRU(e.g., such as a RNTI). The SI may include an indication of thedestination node (e.g., such as a network node (TRP) or another WTRU).The SI may indicate a Cyclic Redundancy Check (CRC) such as a CRCcombined or masked with another field such as the identifier of theWTRU. The SI may indicate the number of codewords. The SI may indicatepower-related information (e.g., such as a power headroom). The SI mayindicate other control information such as scheduling requests and/orbuffer status reports, HARQ-ACK or CSI feedback, and/or transmit powercontrol command.

A WTRU may indicate in SI a description of how information istransmitted for a codeword. The description may in turn include one ormore of following. The description may include a transport channel type.The description may include a coding type such as convolutional orturbo. The description may include a modulation and coding scheme (MCS).The description may include HARQ information such as new data indication(NDI), process identity, and/or retransmission sequence number. Thedescription may include frequency/time allocation within allocatedresources or within a TTI. The description may include spatialprocessing information such as transmit diversity or spatialmultiplexing schemes and/or the number of transmission layers. Thedescription may include antenna ports, and/or reference signalinformation.

A WTRU may use a single field to signal or indicate more than one of theparameters described herein, e.g., to reduce overhead. For example, afield may indicate a combination of MCS and coding type or transportchannel type. A mapping between combination values and values of thecorresponding parameters may be pre-defined or configured by a higherlayer. A WTRU may use one or more of the following techniques toschedule a transmission, and/or set a parameter pertaining to thetransmission.

A WTRU may be configured to multiplex transmissions in a frequency orspace domain. For instance, a WTRU may prioritize the transmission ofdata based on the type of service and/or other parameters such as TTL,as described herein. The WTRU may apply the priority in such a way thatthe start time of higher priority data is earlier than that of lowerpriority data. The WTRU may transmit data of different priorities duringthe same time interval (e.g., under a condition that all data of higherpriority can be transmitted during the time interval). In such a case,higher priority data may be transmitted using a fraction of theavailable resources in the power, frequency and/or space domain.

Available resources may be split in the frequency domain. A WTRU mayallocate as much frequency resources to higher priority data as needed,and use the remaining resources to transmit data of lower priority. TheWTRU may determine frequency allocation for a transmission (e.g., foreach transmission) according to pre-defined rules. For example, the WTRUmay allocate either the highest or the lowest frequency first. Theallocation may be based on frequency-selective channel quality feedbackfrom a receiver and/or based on priorities of the transmission. The WTRUmay allocate the portion of frequency with higher channel quality tohigher priority transmissions first. For instance, the WTRU may havereceived an indication from a network node that a first portion of thefrequency range allocated for self-scheduling operations has higherquality than a second portion. In such a case, the WTRU may perform ahigher priority transmission using at least the first portion of thefrequency range.

If spatial multiplexing can be used, the WTRU may allocate as manytransmission layers to higher priority data as needed, and use theremaining spatial layers to transmit lower priority data. The WTRU maydetermine layer selection for a transmission (e.g., for eachtransmission) according to pre-defined rules or based on layer-specificchannel quality feedback from a receiver, for example.

A WTRU may select transmission power, a MCS, and/or a spatialtransmission scheme according to one or more adaptation principles. Forexample, the WTRU may configure and reconfigure (e.g., adjusted)transmission power. Such transmission power may be expressed, forexample, as a ratio of the maximum transmission power. The WTRU mayconfigure and re-configure (e.g., adjust) the transmission power basedon physical layer signaling, higher layer signaling, or a combinationthereof. To assist with the configuration and re-configuration (e.g.,adjustment), the WTRU may transmit reference signals at a configuredpower level or using a power level signaled by the network. The WTRU mayuse a same transmission power for one or more resource blocks (e.g., foreach resource block). The transmission power may be configured on aresource block basis such that the total transmission power may bedependent on the number of resource blocks on which the transmissiontakes place.

A WTRU may receive an indication of a MCS and/or a coding type to usewith a specific type of data. For example, the WTRU may receive anindication of a first coding type (e.g., convolutional coding), a firstmodulation and coding scheme (e.g., QPSK and rate ⅓), and/or a firstspatial transmission scheme (e.g., transmission diversity such as SFBC)to use for a first type of service (e.g., URLLC). The WTRU may receivean indication of a second coding type (e.g., turbo), a second modulationand coding scheme (e.g., 16-QAM and rate ½), and/or a second spatialtransmission scheme (e.g., spatial multiplexing of rank 2) to use for asecond type of service (e.g., eMBB).

A WTRU may select a MCS and/or a coding type as a function of channelquality feedback from a receiver and/or as a function of the type ofdata to be transmitted. For example, for a given value of channelquality feedback from the receiver, the WTRU may select a first codingtype, a first modulation and coding scheme, and/or a first spatialtransmission scheme if the data to be transmitted corresponds to a firsttype of service (e.g., URLLC). The WTRU may select a second coding type,a second modulation and coding scheme, and/or a second spatialtransmission scheme if the data to be transmitted corresponds to asecond type of service (e.g., eMBB). A mapping between channel qualityfeedback values and the MCS and/or coding type to use for a specifictype of service may be configured by a higher layer.

A WTRU may receive indications of channel quality, MCS and/or code typevia physical layer signaling. For example, the indications may besignaled in downlink control information along with other parametersthat allocate resources for self-scheduling operations. The indicationsmay be signaled on a regular basis (e.g., at an interval that may be inthe order of several TTIs).

A WTRU may adjust its selection of MCS, transmission scheme, and/ortransmission power based on a dynamic indication applicable to a TTI.The WTRU may receive such an indication from a network via physicallayer signaling. For example, a WTRU may select a more conservative MCSlevel and/or transmission scheme if the indication is set to a firstvalue, and may apply a less conservative MCS and/or transmission schemeif the indication is set to a second value. Using the indication, thenetwork may adjust the robustness of transmission, e.g., based onwhether another WTRU is expected to use the same resources in the TTI(e.g., in the case of multi-user MIMO). Using the indication, thenetwork may increase the robustness of transmission after a certainnumber of HARQ retransmissions. The WTRU may map various indications toMCS/transmission scheme combinations. The combinations of MCS's andtransmission schemes may be ranked from the least conservative to themost conservative. For example, the WTRU may store such ranking in atable and an indication may be mapped to an offset that is linked to oneor more entries of the table. The offset may be configured by a higherlayer and/or be dependent on service type or transport channel.

A WTRU may adjust its selection of MCS, coding type, and/or transmissionpower based on the number of retransmissions performed, a delay since aninitial transmission of data, and/or a TTL of the data. For example, theWTRU may apply a more conservative MCS level and/or transmission schemewhen the TTL of the data carried by a transmission falls below athreshold. The adjustment may comprise an offset applied in a table ofMCS's and/or transmission schemes. The adjustment may result inallocating a larger portion of allocated resources to a transmissionwhile increasing the transmission's robustness and probability forsuccessful completion. The WTRU may increase transmission power by anoffset when the TTL of the data falls below a threshold.

A WTRU may be configured to transmit to more than one receiver (e.g.,using more than one MAC instance and/or at the same time). In anexample, a first MAC instance may correspond to a transmission to afirst network node, and a second MAC instance may correspond to atransmission to a second network node. In an example, a first MACinstance may correspond to a transmission to a network node, and asecond MAC instance may correspond to a transmission to another WTRU.The MCS and/or coding type applicable to a transmission (e.g., to eachtransmission) may be dependent on the channel quality feedback and/orother indications provided by a receiver.

Resources may be configured for self-scheduling operations. For one ormore types of services (e.g., for each type of services), theseresources may include one or more of the following. The resources forself-scheduling may include resources for the transmission of dataand/or control information (e.g., SI and/or SCI/UCI). The resources forself-scheduling may include resources for the reception of controlinformation (e.g., downlink or sidelink control information such aschannel quality feedback, HARQ feedback and/or other indications). Theresources for self-scheduling may include parameters for link adaptation(e.g., such as transmission power, offsets for adjustments of power,MCS, and/or transmission schemes). The resources for self-scheduling maybe configured by a higher layer or by a combination of physical layersignaling and higher layer signaling. For example, a WTRU may receive afield, e.g., via downlink control signaling from a physical controlchannel, that may be mapped to a set of parameters associated with theconfiguration of resources for self-scheduling. Such mapping may beconfigured by a higher layer.

A WTRU may have access to resources dedicated for a specific type ofservices (e.g., such as URLLC). Such resources may be common to (e.g.,shared by) multiple WTRUs. The multiple WTRUs may transmit URLLC data(e.g., at least occasionally). The dedicated resources may comprisespecific time/frequency resources such as specific resource blocks orsubcarriers. The resources may be used for a given set of frames orsubframes, or over a long period of time. The WTRU may determine theresources dedicated to a specific service (e.g., for URLLC) based onbroadcast or dedicated signaling by the network, or through an accesstable, for example.

A WTRU may be capable of autonomously transmitting on dedicated PHYresources. For example, the WTRU may be configured to perform suchautonomous transmissions when dedicated PHY resources are reserved forthe WTRU (e.g., only for the WTRU). The WTRU may receive an ACK from thenetwork over a low-latency downlink control channel. For example, theACK may be sent over a control channel. The ACK may be sent within thesame subframe as an indication, and/or through the use of a shortenedTTI. The ACK may include an indication of what resources are to be used.The ACK may be sent over dedicated symbols within certain time frequencyspace (e.g., time frequency space may be reserved for this specificpurpose). For example, a set of symbols may be set aside for a WTRU(e.g., each WTRU) for receiving a downlink ACK. Such symbols may serveother purposes (e.g., the symbols may serve as reference symbols), forexample on the subframes or TTIs in which the WTRU is not expecting aresponse from the indication.

A WTRU may be configured with resources at the PHY layer that may beused (e.g., specifically reserved) for transmissions with shortenedTTIs. For instance, specific time/frequency resources (e.g., x resourceblocks for every y subframes) may be reserved for the WTRU to performshortened TTI transmissions (e.g., 2 OFDM symbols). The WTRU maydetermine the resources reserved for shortened TTI transmissions usingone or more of the following example techniques. The resources may bestatically defined for the WTRU. The resources may be signaled by thenetwork through dedicated signaling or via an access table. Theresources may be defined/created (e.g., implicitly) based on the WTRU'sdevice type, based on service type, and/or based on the type of trafficcurrently managed by the WTRU. The WTRU may be configured to select theresources autonomously.

Certain types of transmissions may be prioritized over others. FIG. 5illustrates an example of prioritizing transmissions. Such transmissionprioritization may be applied in various use cases including thoseinvolving URLLC transmissions, differentiated QoS eMBB transmissions,non-multiplexed URLLC transmissions, and/or the like. Transmissionprioritization may be realized, for example, based on one or more of thefollowing. Transmission prioritization may be realized via requestdifferentiation. Transmission prioritization may be realized viatransport channel selection. Transmission prioritization may be realizedvia re-association of transmission resources to high priority HARQand/or different transport channels. A prioritized transmission mayindicate and/or utilize a specific numerology. A prioritizedtransmission may include a PDU configured with a maximum allowed timefor successfully completing the transmission (e.g., such as in the caseof URLLC transmissions or differentiated QoS eMBB transmissions). Aprioritized transmission may include a PDU associated with a specificlogical channel (e.g., such as in the case of non-multiplexed URLLCtransmission).

As described herein, the example communication system may supportlow-latency communications. A WTRU may be configured to transmitlow-latency packets immediately or with a processing delay (e.g., ashortest possible delay) at the MAC/PHY layers. A WTRU may be configuredto delay transmissions that are already in process, that have beencanceled, and/or that have been terminated to give priority to lowlatency packets. In an example scheme for prioritizing low latencycommunications, a WTRU about to perform a scheduled uplink transmissionmay autonomously decide to delay the scheduled transmission and utilizeresources allocated to the scheduled transmission to transmit orretransmit a transmission with a low-latency requirement.

Examples of transmissions that may be delayed by a WTRU may include adynamically scheduled uplink transmission, a semi-persistenttransmission or a static uplink granted transmission, a scheduledretransmission, and/or the like. In an example, a WTRU having multipleongoing HARQ processes may suspend one of the HARQ processes to allowtransmission of low-latency data. In an example, a WTRU may suspend atransport block or a transmission that is to be retransmitted, andutilize the resources intended for the retransmission to perform aninitial transmission of a transport block or data with low latencyrequirements. In an example, a WTRU may have received a grant associatedwith a transmission of a specific priority, a logical channel, and/or aservice, and the WTRU may decide to utilize the resources intended forthe granted transmission to transmit a low latency packet. For example,a low latency packet may arrive at the MAC layer after a request and acorresponding grant for non-low-latency resources were made. In such ascenario, the WTRU may send an indication to the network regarding thenon-low-latency transmissions for which resources are currentlyreserved, and a different service, priority or logical channel for whichthe WTRU intends the resources to be used instead. The indication may betransmitted using a format and/or technique described herein.

A WTRU may, upon deciding to delay a transmission such as anon-low-latency transmission, transmit an indication to the network thatthe transmission has been delayed in favor of another transmission(e.g., a low-latency transmission). The indication may indicate that agrant or resource allocation is being overwritten. The indication mayindicate the HARQ ID or process associated with the data being delayed.The indication may indicate the HARQ ID or process associated with thenew data. The indication may indicate resources, locations, and/orprocedures that may be used to retransmit the delayed data. Theindication may be provided in the UCI/SCI, SI, and/or RR, as describedherein. The indication may include the type of the data being delayed orto be transmitted. For example, the WTRU may indicate that atransmission is a low-latency transmission, and should be processedaccordingly. The WTRU may indicate the transport format (e.g., MCS,coding, etc.) of the data being transmitted and/or the PHY layerparameters being used to transmit the data over the same resources(e.g., a TTI parameter). A network may, upon receiving the indication,suspend HARQ processing for a particular HARQ process that wasinterrupted. The network may resume the HARQ processing oncetransmission of the low-latency transport block is completedsuccessfully.

Upon prioritizing a new transmission (e.g., a low-latency transmission)over an original transmission, a WTRU may utilize the same modulationand/or coding technique that was intended for the original transmissionfor the new transmission. Alternatively, the WTRU may select a new TTI,modulation and/or coding technique for the new transmission to allow theWTRU to transmit the new transmission within the same resources orwithin parts of the same resources.

The WTRU may send the indication described above to the network using asubset of the resources allocated to the WTRU. For example, WTRU maysend the indication in a transport block, in a set of resource elements,or in a set of subcarriers. The subset of resources may be predefinedfor such a purpose. To illustrate, a WTRU may use the first Nsubcarriers of a first transport block to send the indication. The WTRUmay additionally transmit a predefined sequence to signal to the networkthat the indication is present. Such a technique may allow the networkto first decode dedicated resource elements to determine the presence ofa predefined sequence, a suspension indication, physical layerparameters, and/or the like.

Additionally or alternatively, a WTRU may send the indication describedabove on a separate control channel such as a control channel used forUL low latency control communication. The WTRU may send the indicationon a different set of resources that have a shortened TTI. A network maybe configured to decode the information transmitted by the WTRU blindly.The WTRU may use a UCI/SCI, a UL control channel, SI, or an RR to carrynew scheduling information and/or to indicate new HARQ information, newphysical layer parameters, new SOMs, and/or new TTIs. The WTRU maytransmit the relevant information and/or select the relevant parametersusing one or more of the techniques described herein.

A WTRU may be configured to transmit an RR, SI, and/or low latency datawhile another transmission is ongoing. If an RR is triggered whileanother transmission is ongoing, the WTRU may transmit the RR in themiddle of the ongoing transmission. Within a TTI, certain symbols and/orresources may be reserved for transmitting an RR for time critical data.The WTRU may transmit the RR and/or SI using a CDMA-like signal. TheWTRU may puncture the time critical data and embed the RR request in thedata signal or channel. A receiving entity of the data may receivenotification that the data has been punctured.

When a data transmission is interrupted by an RR and/or time criticaldata, a number of bits (e.g., all bits subsequent to the interruption)may be dropped. A WTRU may embed information in a signal to indicate toa receiving entity that data from a previous transmission were droppedand a new transmission has been started, or that an RR/SI is beingtransmitted. The WTRU may notifying the receiving entity (e.g., anetwork) that data (e.g., all data subsequent to an interruption) weredropped. To handle time critical data, a WTRU may drop a packet from itstransmission buffer or drop a packet it receives from an upper layerbefore the packet is processed by the RAN. The WTRU may be configured todrop packets at any layer. For example, a packet may be dropped when itis received from a higher layer. As another example, a specific layer atthe WTRU may drop an SDU that the WTRU received from a layer above.

When dropping a packet, a WTRU may perform one or more actions. The WTRUmay re-adjust the sequence numbering so that the dropped packet and/orSDU does not occupy a specific sequence number. The WTRU may send aspecific indication (e.g., a MAC CE or a similar control message) withthe transmission to provide an indication of the dropped packet to thenetwork. Example conditions under which a packet may be dropped mayinclude one or more of the following. The WTRU may drop a packet or SDUwhen the packet or SDU arrives later than an expected delivery time. Forexample, the expected delivery time may have already expired when thepacket or SDU arrives. The WTRU may drop a packet or SDU when anexpected processing time (e.g., as expected by the current layers and/orlayers below) of the packet or SDU may cause an expected delivery timeof the packet or SDU to expire before transmission. The WTRU may drop apacket or SDU when the packet or SDU is associated with a logicalchannel, a flow, and/or a service on which packet dropping is allowed.The concerned logical channel, flow, and/or service may be configuredupon initiation to allow packet dropping. The WTRU may drop a packet orSDU when the packet or SDU is multiplexed together with other packetsthat have time critical latency requirements, and the packet or SDUitself does not have time-critical latency requirements.

A WTRU may be configured to transmit an indication to a lower layer, anupper layer, or an application layer that a packet was dropped. Forexample, the WTRU may be configured to transmit an indication to the PHYlayer in order to increase the amount of resources available fortransmission. For example, the WTRU may be configured to notify anapplication layer about potential incorrect operations.

The example communication system described herein may utilize a numberof MAC CEs or MAC layer control messages for MAC layer controlsignaling. One example of such messages may be associated with TRPmodification, including, for example, TRP handover, switching, addition,activation, and/or deactivation. A network may be configured to sendsuch a message to instruct a WTRU to move from Tx/Rx on one TRP to Tx/Rxon another TRP. The message may instruct a WTRU to initiate combinedTX/RX to two different TRPs. The message may comprise one or more of thefollowing fields: target TRP identifier, target TRP configuration (e.g.,resource, power, timers, etc.), target TRP carrier frequency andbandwidth, target TRP RACH or WTRU-autonomous transmissionconfiguration, and/or timing alignment. A WTRU may be previouslyconfigured with a target TRP configuration and may receive an indexand/or a subset of the configuration for accessing the TRP.

Another example MAC CEs or MAC layer control message may be associatedwith a TRP connection request. A WTRU may be configured to send such amessage to request connection to a specific TRP. The message may includeWTRU identification information, a list of logical channels and/orservices, a reason for the connection request, and/or the like.

Another example MAC CEs or MAC layer control message may be associatedwith a TRP measurement list (e.g., the message may comprise a TRPmeasurement list). A network may be configured to provide the WTRU witha list of TRPs that the WTRU should measure. For example, the WTRU maybe instructed to measure the DL quality related to the list of TRPs. Thenetwork may be configured to provide the WTRU with a list of TRPs fromwhich the WTRU should measure a positioning reference signal (PRS)(e.g., for determining the position of the WTRU). The network may beconfigured to provide the WTRU with a list of TRPs to which the WTRUshould maintain UL timing alignment at a given time. The messagecomprising the TRP measurement list may include one or more of thefollowing fields: a message type, a list of TRP identifications (e.g.,an index or similar identifier for each TRP), and/or a thresholdassociated with a TRP (e.g., with every TRP). In an example, informationassociated with the TRP measurement list may be provided as part of theRR and/or SI information.

Another example MAC CEs or MAC layer control message may be associatedwith cross-TRP scheduling configuration. A network may be configured tosend such a message to a WTRU to configure a semi-static cross-TRPscheduling configuration, for example. The message may include one ormore of the following fields: source TRP identification,target/destination TRP identification, and/or resource mapping betweensource and destination resources.

Another example MAC CEs or MAC layer control message may be associatedwith the location of a TRP. A network is configured to send such amessage to a WTRU to provide respective locations of the TRPs that arein the vicinity of the WTRU. The message may include one or more of thefollowing fields: the identification of the TRPs in the vicinity of theWTRU, the system signature used by the TRPs, and/or the respectivelocations of the TRPs.

Another example MAC CEs or MAC layer control message may be associatedwith a timing alignment request. A WTRU may be configured to send such amessage to a network to request the network to provide to the WTRU withUL timing alignment and/or to start a timing alignment procedure. Themessage may include one or more of the following fields: request toenable/disable timing alignment, and the SOM in which timing alignmentis requested.

Another example MAC CEs or MAC layer control message may be associatedwith enhanced timing advance. The message may include one or more of thefollowing fields: an identifier of a TRP, a timing offset associatedwith each TRP, a timing offset associated with each SOM, and/or anindication of allowed/disallowed techniques for uplink timing alignment.

Another example MAC CEs or MAC layer control message may be associatedwith an enhanced buffer status report. The message may include one ormore of the following: a logical channel ID or logical channel group ID,number of bytes in a queue, priority of data, QoS class, one or morepieces of information associated with an RR, transport channel type,number of bytes in a queue having a TTL lower than a first threshold,and/or number of bytes in a queue having a TTL above a threshold, butbelow a second threshold. Different MAC CE may be defined for differentRR types. A MAC CE may comprise a header indicating what RR type the MACCE corresponds to.

Another example MAC CEs or MAC layer control message may be associatedwith a dropped packet indication. Such a message may be sent by a WTRUto a network or by a network to a WTRU to inform a SDU sequencing entityin the WTRU or in a network scheduler of a packet dropping in thesequencing. The message may include one or more of the following fields:a logical channel or flow on which the packet was dropped and/or anindex of the dropped packet (e.g., or indices of a range of droppedpackets).

Another example MAC CEs or MAC layer control message may be associatedwith a SPS configuration. A network may be configured to send such amessage to a WTRU to configure and/or reconfigure semi-persistentlyscheduled resources (e.g., which may be pre-configured) in the WTRU. Themessage may include one or more of the following fields: a resourceidentification (e.g., time, frequency, duration, periodicity, etc.),usage restrictions, an identifier for a resource or identifiers for acollection of resources (e.g., several resource may be configured),and/or the SOM associated with the resource or collection of resources.

Another example MAC CEs or MAC layer control message may be associatedwith SPS resource enabling or disabling. A WTRU may be configured tosend such a message to a network to enable or disable a pre-configuredSPS resource or a collection of SPS resources. The message may includeone or more of the following fields: an indication to enable or disableSPS and/or an identifier for the resource or resource collection.

Another example MAC CEs or MAC layer control message may be associatedwith a resource request, a resource increase or decrease, and/or aresource indication. A WTRU may be configured to send such a message toa network to indicate a request to the network for a specific type ofresources (e.g., a short TTI resource), to request an increase ordecrease in the amount of such allocated resources over time, and/or toindicate to the network that the WTRU is currently utilizing or intendsto utilize a specific resource. The message may include one or more ofthe following fields: a message type, a SOM identification, anincrease/decrease amount, an amount of resources requested, and/or thetype of resources and/or restrictions.

Another example MAC CEs or MAC layer control message may be associatedwith connection reconfiguration. A network may be configured to sendsuch a message to a WTRU to reconfigure a specific connection to a TRP.The message may include one or more the following (e.g., for each SOMconnected to the TRP): new radio configuration, resource configuration,power configuration, timer configuration, and/or the like.

Although features and elements are described above in particularcombinations, one of ordinary skill in the art will appreciate that eachfeature or element can be used alone or in any combination with theother features and elements. In addition, the methods described hereinmay be implemented in a computer program, software, or firmwareincorporated in a computer-readable medium for execution by a computeror processor. Examples of computer-readable media include electronicsignals (transmitted over wired or wireless connections) andcomputer-readable storage media. Examples of computer-readable storagemedia include, but are not limited to, a read only memory (ROM), arandom access memory (RAM), a register, cache memory, semiconductormemory devices, magnetic media such as internal hard disks and removabledisks, magneto-optical media, and optical media such as CD-ROM disks,and digital versatile disks (DVDs). A processor in association withsoftware may be used to implement a radio frequency transceiver for usein a WTRU, UE, terminal, base station, RNC, or any host computer.

What is claimed:
 1. A wireless transmit/receive unit (WTRU), comprising:a processor configured to: receive first configuration information,wherein the first configuration information indicates a first set of oneor more resources to be used by the WTRU for transmitting schedulingrequests associated with a first logical channel; receive informationindicating an uplink transmission grant for the WTRU; determine thatdata associated with the first logical channel is available fortransmission; determine that a subcarrier spacing associated with theuplink transmission grant is not among one or more subcarrier spacingsassociated with the first logical channel; and responsive to determiningthat the subcarrier spacing associated with the uplink transmissiongrant is not among the one or more subcarrier spacings associated withthe first logical channel, transmit a scheduling request for the dataassociated with the first logical channel using the first set of one ormore resources indicated in the first configuration information.
 2. TheWTRU of claim 1, wherein the processor is further configured to receivesecond configuration information indicating that a second set of one ormore resources is to be used for transmitting scheduling requestsassociated with a second logical channel.
 3. The WTRU of claim 1,wherein the processor is further configured to determine that the uplinktransmission grant is associated with a second logical channel based ona transmission timing parameter associated with the second logicalchannel or a numerology parameter associated with the second logicalchannel.
 4. The WTRU of claim 1, wherein the processor is furtherconfigured to determine that the uplink transmission grant is associatedwith a second logical channel based on a determination that thesubcarrier spacing associated with the uplink transmission grant isamong one or more subcarrier spacings associated with the second logicalchannel.
 5. The WTRU of claim 4, wherein the first logical channel andthe second logical channel are associated with a same serving cell. 6.The WTRU of claim 1, wherein the processor is further configured toreceive information indicating a type of service for which the uplinktransmission grant is to be used.
 7. The WTRU of claim 6, wherein theinformation that indicates the uplink transmission grant for the WTRUfurther indicates the type of service for which the uplink transmissiongrant is to be used.
 8. The WTRU of claim 1, wherein the firstconfiguration information further indicates the one or more subcarrierspacings associated with the first logical channel.
 9. The WTRU of claim1, wherein the processor is further configured to determine that theuplink transmission grant is associated with a second logical channel,and wherein the first logical channel and the second logical channel areassociated with respective transmission priorities or quality of service(QoS) requirements.
 10. The WTRU of claim 9, wherein at least one of thetransmission priorities or QoS requirements is associated withultra-reliable and low latency communications (URLLC).
 11. A methodimplemented in a wireless transmit/receive unit (WTRU), the methodcomprising: receiving first configuration information, wherein the firstconfiguration information indicates a first set of one or more resourcesto be used by the WTRU for transmitting scheduling requests associatedwith a first logical channel; receiving information indicating an uplinktransmission grant for the WTRU; determining that data associated withthe first logical channel is available for transmission; determiningthat a subcarrier spacing associated with the uplink transmission grantis not among one or more subcarrier spacings associated with the firstlogical channel; and responsive to determining that the subcarrierspacing associated with the uplink transmission grant is not among theone or more subcarrier spacings associated with the first logicalchannel, transmitting a scheduling request for the data associated withthe first logical channel using the first set of one or more resourcesindicated in the first configuration information.
 12. The method ofclaim 11, further comprising receiving second configuration informationindicating that a second set of one or more resources is to be used fortransmitting scheduling requests associated with a second logicalchannel.
 13. The method of claim 11, further comprising determining thatthe uplink transmission grant is associated with a second logicalchannel based on a transmission timing parameter associated with thesecond logical channel or a numerology parameter associated with thesecond logical channel.
 14. The method of claim 11, further comprisingdetermining that the uplink transmission grant is associated with asecond logical channel based on a determination that the subcarrierspacing associated with the uplink transmission grant is among one ormore subcarrier spacings associated with the second logical channel. 15.The method of claim 14, wherein the first logical channel and the secondlogical channel are associated with a same serving cell.
 16. The methodof claim 11, further comprising receiving information that indicates atype of service for which the uplink transmission grant is to be used.17. The method of claim 16, wherein the information that indicates theuplink transmission grant for the WTRU further indicates the type ofservice for which the uplink transmission grant is to be used.
 18. Themethod of claim 11, wherein the first configuration information furtherindicates the one or more subcarrier spacings associated with the firstlogical channel.
 19. The method of claim 11, further comprisingdetermining that the uplink transmission grant is associated with asecond logical channel, wherein the first logical channel and the secondlogical channel are associated with respective transmission prioritiesor quality of service (QoS) requirements.
 20. The method of claim 19,wherein at least one of the transmission priorities or QoS requirementsis associated with ultra-reliable and low latency communications(URLLC).